V4L/DVB (8868): gspca: Support for vga modes with sif sensors in sonixb.

- Add documentation for some known registers
- Add support for vga modes (320x240, 160x120) for sif sensors
- Remove F_RAW sensor flag raw mode should work on any sensor as its a bridge
   only thing and keeping the flag was becoming awkward.
- Fixup ov6650 and pas106 auto exposure window settings

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@redhat.com>