Update quantum matrix to support both AVR and Chibios ARM (#3968)
* Update quantum matrix to support both AVR and Chibios ARM
- Addition of STM32 pin definitions
- Created abstruction layer defines to control GPIO (This is a bit pointless for Chibios as we are creating a PAL ontop of a PAL but it is necessary for uniformity with AVR)
- Modified matrix.c to use the above functions
* minor ifdef fix
* Rename of functions and docs
- Added documentation.
- Renamed functions according to Jack's spec.