media: ov2685: add support for OV2685 sensor

This patch adds driver for Omnivision's ov2685 sensor.
Though the ov2685 can output yuv data, this driver only
supports the raw bayer format, including the following features:
  - output 1600x1200 at 30fps
  - test patterns
  - manual exposure/gain control
  - vblank and hblank
  - media controller
  - runtime pm

[Sakari Ailus: trivial: ov5695_of_match -> ov2685_of_match]

Signed-off-by: Shunqian Zheng <zhengsq@rock-chips.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>