Remove support for the debug call VIDIOC_INT_S_AUDIO_ROUTING from cx18
and ivtv. These internal ioctls shouldn't be exposed. These were only
used through the cx18-ctl and ivtv-ctl utilities, and only when testing
a new card variant.

This cleanup allows the removal of this ioctl from v4l2-common.h.

Cc: Andy Walls <awalls@radix.net>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>