ARM: dts: stm32: add CAN support on stm32f746

Add support for bxcan (Basic eXtended CAN controller) to STM32F746. The
chip contains three CAN peripherals, CAN1 and CAN2 in dual peripheral
configuration and CAN3 in single peripheral configuration:
- Dual CAN peripheral configuration:
  * CAN1: Primary bxCAN for managing the communication between a secondary
    bxCAN and the 512-byte SRAM memory.
  * CAN2: Secondary bxCAN with no direct access to the SRAM memory.
  This means that the two bxCAN cells share the 512-byte SRAM memory and
  CAN2 can't be used without enabling CAN1.
- Single CAN peripheral configuration:
  * CAN3: Primary bxCAN with dedicated Memory Access Controller unit and
    512-byte SRAM memory.

 -------------------------------------------------------------------------
| features | CAN1              | CAN2               | CAN 3               |
 -------------------------------------------------------------------------
| SRAM     | 512-byte shared between CAN1 & CAN2    | 512-byte            |
 -------------------------------------------------------------------------
| Filters  | 26 filters shared between CAN1 & CAN2  | 14 filters          |
 -------------------------------------------------------------------------

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Link: https://lore.kernel.org/all/20230427204540.3126234-6-dario.binacchi@amarulasolutions.com


Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>