can: m_can: Removed initialization of FIFO water marks

FIFO water marks disabled because the driver doesn't handle water mark
events.

Signed-off-by: Mario Huettel <mario.huettel@gmx.net>
Reviewed-by: Oliver Hartkopp <socketcan@hartkopp.net>
Tested-by: Quentin Schulz <quentin.schulz@free-electrons.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>