[media] stk1160: Add support for S-Video input

In order to fully replace easycap driver with stk1160,
it's also necessary to add S-Video support.
A similar patch backported for v3.2 kernel has been
tested by three different users.

Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>