can: dev: register_candev(): bail out if both fixed bit rates and bit timing constants are provided

The CAN driver framework supports either fixed bit rates or bit timing
constants. Bail out during driver registration if both are given.

Link: https://lore.kernel.org/all/20230202110854.2318594-7-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>