Fix misc compile warnings

Fix misc compile warnings

Shut up misc compile warnings from gcc:
  pcm_plug.c: In function ‘snd_pcm_plug_change_mmap’:
  pcm_plug.c:608: warning: enumeration value ‘SND_PCM_ACCESS_MMAP_INTERLEAVED’ not handled in switch
  pcm_plug.c:608: warning: enumeration value ‘SND_PCM_ACCESS_MMAP_NONINTERLEAVED’ not handled in switch
  pcm_plug.c:608: warning: enumeration value ‘SND_PCM_ACCESS_MMAP_COMPLEX’ not handled in switch

Signed-off-by: Takashi Iwai <tiwai@suse.de>