The audio clients have to be disabled before disabling the VGA and
switching.  Similarly, enabling the audio client should be done at
last.  Otherwise the audio-side operation stalls, eventually leading
to Oops or lockups.
Tested-by: NJörg-Volker Peetz <jvpeetz@web.de>
Acked-by: NDave Airlie <airlied@redhat.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>