media: i2c: cap exposure at height + vblank in ov8865

Exposure limits depend on the total height; when vblank is altered (and
thus the total height is altered), change the exposure limits to reflect
the new cap.

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>