Volume knob controls with STAC codecs seem to cause problems with some
devices.  Volumes change very slowly or silent suddenly.  It's likely
due to conflict between the software and the hardware volume knob
setup.
Since we'll have a virtual master control in future, it's safer to
remove this control completely right now.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>