V4L/DVB (5769): Ivtv: fix broken VBI output support

The old service_set_out setting was still tested, even though it no longer
was ever set and was in fact obsolete. This meant that everything that was
written to /dev/vbi16 was ignored. Removed the service_set_out variable
altogether and now it works again.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>