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.

arch/arm/kinetis:  Still moving register header files to kinetis/chip directory; still incorporating K64 differences.

arch/arm/kinetis:  Still moving register header files to kinetis/chip directory; still incorporating K64 differences.

arch/arm/kinetis:  Still moving register header files to kinetis/chip directory; still incorporating K64 differences.