can: at91_can: add CAN transceiver support

Add support for Linux-PHY based CAN transceivers.

Link: https://lore.kernel.org/all/20231005-at91_can-rx_offload-v2-16-9987d53600e0@pengutronix.de


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