Fix the following lockdep warning by not reusing the hda_codec.spdif_mutex.

    ALSA sound/pci/hda/hda_codec.c:882: hda_codec_cleanup_stream: NID=0x2

    =======================================================
    [ INFO: possible circular locking dependency detected ]
    2.6.28-next-20090102 #33
    -------------------------------------------------------
    mplayer/3151 is trying to acquire lock:
     (&pcm->open_mutex){--..}, at: [<ffffffffa004ced3>] snd_pcm_release+0x43/0xd0 [snd_pcm]

    but task is already holding lock:
     (&mm->mmap_sem){----}, at: [<ffffffff810c0252>] sys_munmap+0x42/0x80

    which lock already depends on the new lock.
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>