[media] gspca-stk1135: Add variable resolution support

Add variable resolution support to Syntek STK1135 subdriver.

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>