V4L/DVB (9283): Correct typo and enable setting the gain on the mt9m111 sensor

A typo was introduced during the gspca conversion, crippling the ability to control the gain on the mt9m111 sensor.

Signed-off-by: Erik Andrén <erik.andren@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>