media: ov5640: Add register definition for test pattern register

The OV5640 can generate many types of test patterns, some with
additional modifiers, such as a rolling bar, or gamma gradients.

Add the bit definitions for all bits in the test pattern register,
and use them to compose the values to be written to the register.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>