V4L/DVB (8366): gspca: Better code for ov6650 and ov7630.

sonixb:   Common code between ov6650 and ov7630.
          Fix brightness oscillation with ov6650 sensor.

Signed-off-by: Hans de Goede <j.w.r.degoede@hhs.nl>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>