The master mute switch is wrongly implemented as checking the pointer
instead of its value, thus it can be never muted.  This patch fixes
the issue.

Reference: Novell bnc#404873
	https://bugzilla.novell.com/show_bug.cgi?id=404873Signed-off-by: Takashi Iwai <tiwai@suse.de>
Cc: <stable@kernel.org>