[media] radio-si4713: remove audout ioctls

The audout ioctls are not appropriate for radio transmitters, they apply to
video output devices only. Remove them from this driver.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Eduardo Valentin <edubezval@gmail.com>
Tested-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>