cdcacm_unbind leaks write request objects.  This arises due to freeing the

bulk IN endpoint before the loop that frees the requests via cdcasm_freereq.
That function checks the parameters and skips the freeing if either is NULL.
Freeing the bulk IN enpoint will cause the first param to be NULL, thereby
bypassing the free operation.  To fix, I moved the release of the bulk IN
endpoint until after to loop (much as was the case for the OUT and read
requests, which did not exhibit the problem).

STM32 timer. More clean up:  Add all function prototypes.  Reorder functions to match ordering in operations structure.

STM32:  Various fixed to get a clean compile after integrating tickless mode.  Mostly because patch came from an old version of NuttX.

ioexpander/gpio: Add missing argument to gpin_read and gpout_read

Freedom K64F: Add board_initialize() hooks and bringup C file like more contemporary board configurations

Freedom K64F:  Correct comments about VCOM serial console.  Add pin multi-plexing disambiguaration for the VCOM UART pins.

Add support for the NXP Freedom-K64F board.  This is primarily the work of Jordan Macintyre.  I leveraged this code from https://github.com/jmacintyre/nuttx-k64f

arch/arm/kinetis:  Completes moving register header files to kinetis/chip directory with all K64 changes.