[media] saa7134: v4l2-compliance: remove bogus audio input support

Make saa7134 driver more V4L2 compliant: remove empty g_audio and s_audio
functions and don't set audioset in enum_input

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>