can: rcar_canfd: rcar_canfd_channel_probe(): register the CAN device when fully ready

Register the CAN device only when all the necessary initialization is
completed. This patch makes sure all the data structures and locks are
initialized before registering the CAN device.

Link: https://lore.kernel.org/all/20220221225935.12300-1-prabhakar.mahadev-lad.rj@bp.renesas.com


Reported-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Pavel Machek <pavel@denx.de>
Reviewed-by: Ulrich Hecht <uli+renesas@fpond.eu>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>