media: mt9m111: add V4L2_CID_TEST_PATTERN control

The mt9m111 has the test pattern generator features.  This makes use of
it through V4L2_CID_TEST_PATTERN control.

Cc: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>