PIOS COM: make the interface thread safe

Currently the interface to the FIFO buffer is not thread
safe for multiple threads sending and receiving. This adds
a semaphore on those interfaces.
Android: add serial support for FTDI_FT230X

This is the chipset used in the 3dr radio v2 and should
add support for that radio.
Merge pull request #1187 from peabody124/ftdi_pid

Android: add serial support for FTDI_FT230X
Merge pull request #1181 from peabody124/pios_com_thread

PIOS COM: make the interface thread safe