media: mt9m111: No need to check for the regulator

The regulator_get() function returns a regulator when it succeeds. There's
no need to check whether the regulator is NULL later on.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>