The commit [9bef72bdb26e: ALSA: pcxhr: Use nonatomic PCM ops]
converted to non-atomic PCM ops, but shamelessly with an unbalanced
mutex locking, which leads to the hangup easily. Fix it.
Fixes: 9bef72bdb2 ('ALSA: pcxhr: Use nonatomic PCM ops')
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=116441
Cc: <stable@vger.kernel.org> # 3.18+
Signed-off-by: Takashi Iwai <tiwai@suse.de>