V4L/DVB: au8522_decoder: g/s_fmt doesn't do anything: remove

g/s_fmt is going to disappear, so if it is not doing anything, then
just remove it.

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