iMX6 devices: Switch powersupply for CAN/RS485 on demand

Address problems from "SANTINO: RS485 and CAN communication does not work" (746-001165):

• enable CAN/RS485 transmitters;
• add control of RS485 transmitter (receiving/transferring) via GPIO.

Notes:

• several commits from linux-5.10.104-guf were not ported to 5.15.29-guf:
  • linux-guf@de594182
  • linux-guf@86c13f7a
• although we found and ported fixes from the old BSP, CAN/RS485 does not work on our Santino both in the old and existing BSPs. As we can't debug the issue further without oscilloscope, we assume that it's a malfunction of particular board.