media: ov7670: Add entity pads initialization

Add the media entity pads initialization.

Signed-off-by: Wenyou Yang <wenyou.yang@microchip.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>