[media] au0828: fix initial video routing

After loading the module the initial video routing is not setup.
Explicitly call s_input to get this right.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>