can: flexcan: fix spelling mistake "reserverd" -> "reserved"

Fix a mistake in a register layout description.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200214141751.21168-1-alexandre.belloni@bootlin.com


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