V4L/DVB: gspca - zc3xx: Change the resolutions of some sensors

The sensors adcm2700, mc501cb and ov7620 cannot have the full height
permitted by the zc3xx bridges. This change removes 8 pixels at the
bottom of the images.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>