[CAN bus] update
- use `struct CAN_frame`
- add CAN baud rate enums
- make CAN0 basic the primary actor
- add CAN0_latest() to CAN0 basic
- add CAN0_poll() to CAN0 basic
[SPI0] no need for SPI0 stuff
[MAX7301] code for port expanders
[M95256] update to use struct M95256
- mock SPI device with
-- chip select/deselect methods
-- byte exchange method
[MAX3100] fixes forgotten during porting
- misnamed RX/TX byte ring's