V4L/DVB (8455): gspca_sonixb sn9c103 + ov7630 autoexposure and cleanup

Andoni Zubimendi has been doing some testing with his sn9c103 cam with
ov7630 sensor, and with this patch the exposure setting and autoexposure now
work.

This patch also removes some special cases in the shared ov6650 / ov7630 code
which now are handled the same for both sensors and it adds a new special case
which stops us from changing the hsync / vsync polarity settings from their
default on the ov7630 (which we were doing as a side-effect of using the ov6650
exposure code for the ov7630).

Last this patch removes the superficial difference between the OV7630 and
OV7630_3 sensors.
Signed-off-by: Andoni Zubimendi <andoni.zubimendi@gmail.com>
Signed-off-by: Hans de Goede <j.w.r.degoede@hhs.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>