media: uvcvideo: Add support for the CNF4 format

Register the GUID used by Intel RealSense cameras with fourcc CNF4,
encoding depth sensor confidence information for every pixel.

Signed-off-by: Sergey Dorodnicov <sergey.dorodnicov@intel.com>
Signed-off-by: Evgeni Raikhel <evgeni.raikhel@intel.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>