[media] au0828: enable VBI timeout when calling read() without streamon()

Because some clients (e.g. tvtime) will just open the filehandle and call
read() instead of explicitly calling streamon first, we need to make sure the
VBI timeout routine gets enabled in this case.

Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>