Remove unused STM32 USB libraries

This was a duplicate library.  The proper one lives underneath stm32_base/libs
Merge branch 'mk2' of github.com:autosportlabs/RaceCapture-Pro_firmware into mk2
WIP: Working USB FS port for serial emulation

This heavily leans on ST's existing code.  Still needs decoupled from
the interrupt and re-thinking the transmit path