Add the image quality bridge controls contrast, brightness, saturation,
blue balance, red balance and sharpness.
These controls are enabled only if no subdevice provides them.
Tested with the following devices:
"Terratec Cinergy 200 USB"
"Hauppauge HVR-900"
"SilverCrest 1.3MPix webcam"
"Hauppauge WinTV USB2"
"Speedlink VAD Laplace webcam"
Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>