[media] media: ov5670: Use recommended black level and output bias

Previously, images were relatively darker due to non-optimal
settings for black target level and bias.

Now, use recommended settings for black target level and output bias
as default values. The same default settings apply to all the resolutions.
Given these recommeneded settings do not change dynamically, add these to
existing mode register settings.

Signed-off-by: Chiranjeevi Rapolu <chiranjeevi.rapolu@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>