media: i2c: Add ov9734 image sensor driver

Add a v4l2 sub-device driver for the OminiVision ov9734 image sensor
which can deliver maximum 720p image frames at 30 fps. This driver
also add vertical blanking, exposure, test pattern, digital and analog
gain control for the image sensor.

Signed-off-by: Bingbu Cao <bingbu.cao@intel.com>
Signed-off-by: Tianshu Qiu <tian.shu.qiu@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>