can: rcar_canfd: Add transceiver support

Add support for CAN transceivers described as PHYs.

While simple CAN transceivers can do without, this is needed for CAN
transceivers like NXP TJR1443 that need a configuration step (like
pulling standby or enable lines), and/or impose a bitrate limit.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/all/1ce907572ac1d4e1733fa6ea7712250f2229cfcb.1679414936.git.geert+renesas@glider.be


[mkl: squash error message update from patch 2]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>