ALSA: pcm: Use recursive mutex

ALSA: pcm: Use recursive mutex

The recent thread-safety pthread implementation caused deadlocks in
some situations, e.g. when an external plugin calls snd_pcm_state() in
its callback.  One can avoid the deadlock by carefully using the
unlocked version, but it's often error-prone, and it might be still
problem with the old binaries.

In this patch, we initialize the pthread mutex as recursive for fixing
such a problem.

Suggested-by: Timo Wischer <twischer@de.adit-jv.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>