media: i2c: Add vblank control to ov8865

Add a V4L2_CID_VBLANK control to the ov8865 driver.

Signed-off-by: Daniel Scally <djrscally@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>