dt-bindings: mfd: stm32f7: Add binding definition for CAN3

Add binding definition for CAN3 peripheral.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Link: https://lore.kernel.org/r/20230423172528.1398158-2-dario.binacchi@amarulasolutions.com


Signed-off-by: Lee Jones <lee@kernel.org>