mx31moboard: fix typo

Currently, linux-next breaks due to a typo introduced in commit
33c4d919



This patch fixes it.

Signed-off-by: Robert Schwebel <r.schwebel@pengutronix.de>
Cc: Valentin Longchamp <valentin.longchamp@epfl.ch>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>