V4L/DVB (8197): gspca: pac207 frames no more decoded in the subdriver.

videodev2: New pixfmt
pac207:   Remove the specific decoding.
main:     get_buff_size operation added for the subdriver.

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>