wireless/bluetooth:  Remove Rx kernel thread.  The operation of dispatching messages can be performed just as well on the high and low priority work queue.  The network driver operates the low priority work queue so that also integrates better with network frame reception.

Xbee: Adds a timeout to send logic to handle case where XBee module fails to respond to a Transmit request with a Transmit Status

Approved-by: Gregory Nutt <gnutt@nuttx.org>

stm32f7 fix CONFIG_STM32F7_STM32F77X define typo

Approved-by: Gregory Nutt <gnutt@nuttx.org>

arch/arm/include/tms570, arm/src/armv7-r, and arm/src/tms570:  Adds support for the TMS570LS3137ZWT and corrects seversl ARMv7-R and TMS570 issues

arch/arm/src/stm32 and drivers/wireless/bluetooth:  Fix some buffer management errors in HCI UART upper and lower halves.

net/sixlowpan:  Fix a nasty, byte-ordering/endian-ness problem.  The root cause has been found and corrected.  And a half dozen or so bandaid fixes were reverted.

drivers/wireless/bluetooth: Default BAUD must be 115200, Fix logic in Rx callback, Rx callback must execute on work queue.  Now sends and receives one command and response.  But hangs on the next.

arch/arm/src/imxrt:  Corrects error in serial interrupts and baud setup.  Now the baseic IMXRT1050-EVK port is ready. The console is working.

arch/arm/src/stm32/:  In HCI UART, sense of RTS and CTS are inverted.  When we speak of asserting RTS we mean setting nRTS to zero.

arch/arm/src/stm32 and configs/stm32f4discovery:  Some feeble attempts to communicate with the BT860.  Not much progress yet.

net/sixlowpan: Simplify redundant check in the previous commit.  If fullmac == true, then we must also have usemac == true and so checking usemac in that context is redundant.

arch/arm/src/imxrt:  Fix problem with with CPU hanging during boot in the clockconfig function.  configs/imxrt1050-evk/scripts:  Update linker script so that the NXP boot header will be included in the build.

net/sixlowpan:  When uncompressing link local addresses, the source of the address matters.  Apparently address by byte reversed in IP addresses.  But if the source of the address is the locally assigned address, bytes are not reversed.

Revert "net/sixlowpan:  Fix a constant value used in IPv6 address decompression.  The 0x0200 value used in the address modification should be in network order."

This reverts commit e8832be8.

wireless/bluetooth:  Soften use of enter_critical_sectino() which is a performance hog in SMP configurations.  Replace with spin_lock_irqsave() in most cases.  That is the same for single core CPUs, but much more efficient in SMP configurations.  And better, repace with sched_lock() if there is really no necessity to disable interrupts too.

tools/mkromfsimg.sh:  Include an option in mkromfsimg.sh to ignore FAT/RAMDISK. This permits you to build tiny systems with ROMFS but with the rather large FAT FS support.

fs/mount:  Fix wrong size reported by df -h.  Reason is that size in bytes is calculated always on uint32_t types and cards bigger than 4GB will overflow uint32_t type. Solution is to use uint64_t where possible.

wireless/bluetooth:  Use nxsem_timedwait() vs nxsem_wait() when waiting for response from the HCI device.  Adding this timeout prevents things from hanging when there is a problem with the connect HCI UART (in the current test, when there is no HCI UART connected).

wireless/bluetooth and drivers/wireless/bluetooth:  Simply the driver registration/initialization interface.

arch/arm/src/stm32:  In HCI UART driver, need to disable Tx interrupts after frame sent.  Otherwise, we get infinite Tx interrupts.

Various fixes/changes from intial testing of the HCI UART on the STM32F4-Discovery board.  Re-organized how the Blutetooth network driver is initialized.  Added lots of new debug output.  Add a new STM32 F4 Discovery configuration for testing the HCI UART.  Various fixes to get through initialization (still does not).

fs/smartfs:  Fix a hardfault in SmartFS.  Problem occurred when opening a file with O_CREAT (only) when the file arelready exists but has a size of zero.

configs/stm32fdiscovery:  Add support in bringup logic to initialize the HCI UART and register the HCI UART network device.

configs/imxrt1050-evk:  This commit adds support for booting from the on board HYPER Flash. I placed the boot and flash files in the /configs/imxrt1050-evk/ , because I thing they are board related, so for other board or other flash this files has to be changed.  So far I verified that the __start function is called and the code is executing from flash, but still the rest of the code is not tested.

Squashed commit of the following:

    arch/arm/src/stm32:  Add Kconfig options needed by the HCI UART.  Various fixes to finally get a clean error free compile with no unexpected warnings.
    arch/arm/src/stm32:  In HCI UART, use spin_lock_irqsave() instead of enter_critical_section() whenever possible.
    arch/arm/src/stm32:  In HCI UART, fix up naming of configurations so that they are unique.  Still needs Kconfig settings.  Modify logic so that there can be multiple HCI UARTs, some supporting DMA and some not.
    arch/arm/src/stm32:  Integrate watermarks and software Rx flow control into the HCI UART driver.
    arch/arm/src/stm32:  Eliminate some HCI UART UART configuration options.  Per the HCI UART spec, the link will b 8 data bits, no parity, 1 stop bit... Always.
    arch/arm/src/stm32:  Trivial cleanup
    arch/arm/src/stm32:  Fixes most initial compilation issues STM32 HCI UART driver.  Still need to set up USART configuration parmeters for HCI UART
    arch/arm/src/stm32:  Completes first cut at STM32 HCI UART driver.
    arch/arm/src/stm32:  Completes most of read logic for HCI UART.  Still needs to be able to block if no read data is available.  Still missing write and flush logic.
    drivers/wireless:    Remove txenable from HCI UART methods.  arch/arm/src/stm32:  Reorganize some structures in HCI UART.
    arch/arm/src/stm32:  Still messaging the HCI uart driver.
    arch/arm/src/stm32:  Some trivial renaming.
    arch/arm/src/stm32:  A little more HCI-UART logic.
    arch/arm/src/stm32:  Initial setup to support HCI-UART.  Little more than the serial driver with some name changes and a few things removed.

net/sixlowpan:  Fix a constant value used in IPv6 address decompression.  The 0x0200 value used in the address modification should be in network order.

Change ordering of round-robin time slice check (sched_process_scheduler()) and processing of wdog timers (wd_timer()).  wd_timer()'s callback function can change current running task and, hence, must be done after the time slice check.

The time slice check will decrement the currently running task's time slice allotment.  If such a context switch occurs, then the newly started task will lost one could of that allotment before it even has a chance to run.

This commit brings in basic support fo the i.MX RT 1050 'crossover' SoC.  The basic support is complete and compiles without error, but is still untested.

This port was the joing effort of Janne Rosberg, Ivan Ucherdzhiev, and myself.  I give credit to Ivan for the kill because he is the one to held on to the end.

Squashed commit of the following:

  Author: Gregory Nutt <gnutt@nuttx.org>
    configs/imxrt1050-evk/scripts:  Add section to linker script to handle the case where RAMFUNCs are enabled.  RAMFUNCs appear to be enabled in the default configuration ... they probably should not be enabled.

  Author: Ivan Ucherdzhiev <ivanucherdjiev@gmail.com>
    arch/arm/src/imxrt:  imxrt_lowputc.c is finished. Now everything needed for the initial port is done and ready for testing.
    arch/arm/src/imxrt:  Add logic to imxrt_lowputc.c.  Still incomplete.

  Author: Ivan Ucherdzhiev <ivanucherdjiev@gmail.com>
    arch/arm/src/imxrt:  Add serial support.  configs/imxrt1050-evk:  Add linker script.

  Author: Gre...