The valid values for these controls are 0..3 (lower two bits) which was
identified by trial and error on Labtec Webcam 2200 (USB ID 093a:2626).
The upper 6 bits are ignored on page 0, registers 0xc5 and 0xc7 by the camera.

Signed-off-by: Márton Németh <nm127@freemail.hu>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>