[media] media: mt9p031/mt9t001/mt9v032: use V4L2_CID_TEST_PATTERN for test pattern control

V4L2_CID_TEST_PATTERN is now a standard control.
This patch replaces the user defined control for test
pattern to make use of standard control V4L2_CID_TEST_PATTERN.

Signed-off-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Signed-off-by: Manjunath Hadli <manjunath.hadli@ti.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>