The makes for cleaner board definitions like:

   Divider output clock = Divider input clock * ((PLLFLLFRAC+1)/(PLLFLLDIV+1))
       SIM_CLKDIV3_FREQ = BOARD_SOPT2_FREQ × [ (PLLFLLFRAC+1) / (PLLFLLDIV+1)]
                 90 Mhz = 180 Mhz X [(0 + 1) / (1 + 1)]
    #define BOARD_SIM_CLKDIV3_PLLFLLFRAC  1
    #define BOARD_SIM_CLKDIV3_PLLFLLDIV   2
    #define BOARD_SIM_CLKDIV3_FREQ        (BOARD_SOPT2_FREQ * (BOARD_SIM_CLKDIV3_PLLFLLFRAC / BOARD_SIM_CLKDIV3_PLLFLLDIV))

  The warning has been added because: SIM_SOPT2_PLLFLLSEL
  is a clock selection that may feed many clock subsystem:
   USB, TPM, SDHCSRC, LPUARTSRC. Therefore, there needs to
  be a global board level setting to select  the source for
  SIM_SOPT2_PLLFLLSEL and then  derive all the  sub selections
  and proper fractions/divisors for each modules clock.

   ACKISO is located in the PMC_REGSC on the majority
   of the Kinetis SoCs. With the exception of the
   MK40DXxxxZVLQ10 where ACKISO is located in LLWU_CS

  ACKISO is located in the PMC_REGSC on the majority
  of the Kinetis SoCs. With the exception of the
  MK40DXxxxZVLQ10 where ACKISO is located in LLWU_CS

     The motvations is to version the IP blocks of the Kinetis
     K series family of parts.

     This added versioning and configuration features for the
     Kinetis PMC IP block.

     It is envisioned that in the long term as a chip is added.
     The author of the new chip definitions will either find
     the exact configuration in an existing chip define and
     add the new chip to it Or add the PMC fature configuration
     #defines to the chip ifdef list in
     arch/arm/include/kinetis/kinetis_pmc.h  In either case the
     author should mark it as "Verified to Document Number:"
     taken from the reference manual.

     The version KINETIS_PMC_VERSION_UKN has been applied to
     most all the SoCs in the kinetis arch prior to this commit.

     The exceptions are the CONFIG_ARCH_CHIP_MK60FN1M0VLQ12,
     CONFIG_ARCH_CHIP_MK20DXxxxVLH7 All K64 and K66 have ben
     Verified PMC configurations.

   The motvations is to version the IP blocks of the Kinetis
   K series family of parts.

   This added versioning and configuration features for the
   Kinetis SIM IP block.

   It is envisioned that in the long term as a chip is added.
   The author of the new chip definitions will either find
   the exact configuration in an existing chip define and
   add the new chip to it Or add the SIM feature configuration
   #defines to the chip ifdef list in
   arch/arm/include/kinetis/kinetis_sim.h  In either case the
   author should mark it as "Verified to Document Number:"
   taken from the reference manual.

   The version KINETIS_SIM_VERSION_UKN has been applied to
   most all the SoCs in the kinetis arch prior to this commit.

   The exceptions are the CONFIG_ARCH_CHIP_MK60FN1M0VLQ12,
   All K64 and K66 which not have Verified SIM configurations.

fstatfs: Rethink last commit.  Add verification that the file descriptor refers to an open file.  This also should eliminate the warning while doing something useful.

Fixes warning and file name

Approved-by: Gregory Nutt

Removed CONFIG_LIBC_ARCH_BZERO.  bzero() is a deprecated interface.  There are no architecture-specific replacements and, if there were, they should replace memset(), not bzero().

This should resolve issue #30: Audio Tone Generator and PWM Multiple Output Channel options.  I don't actually have a setup to verify it, however.

STM32F7 has up to 128KiB of DTCM memory that is currently left unused.

This patch adds DTCM to main heap if CONFIG_STM32F7_DTCMEXCLUDE is not enabled.

Add twr-k64f120m config and fix some ENET related problems

Approved-by: Gregory Nutt

Add driver for the ST L3GD20 3 axis gyro

Approved-by: Gregory Nutt