V4L/DVB: gspca_ov519: Don't report a saturation control for 7670 sensors

setcolors(0 is a no-op for 7670 sensors, so we should not report a
saturation control for 7670 sensors.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>