Experimental "USB to CANbus bridge" mode

[koconnor]

@zannys

i found (i think) a bug, if i select pins PB13, 12 (Skr pro v1.1 or Fly Gemini v2) to use as CAN, just not work, but if i choose PB8, 9 Can works fine. I dont know if have any reletion but reading datasheet (Stm32F407 and F405) PB13, 12 is listed as CAN_2 and PB8, 9 as CAN_1

An error was found in the CAN2 handling on stm32f4 boards - see MKS SKIPR CAN Bus - #80 by koconnor

-Kevin