V4L/DVB (8348): gspca: Add auto gain/exposure to sonixb and tas5110 / ov6650 sensors.

sonixb:   Do auto gain for tas5110 / ov6650 sensors.
pac207:   Move the auto_gain function to gspca.
gspca:    New function gspca_auto_gain_n_exposure().

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>