V4L/DVB (13993): gspca.txt: add cams supported by mr97310a, sq905(c) and sn9c2028 drivers

gspca.txt: add cams supported by mr97310a, sq905(c) and sn9c2028 drivers

Signed-off-by: Theodore Kilgore <kilgota@banach.math.auburn.edu>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>