ALSA: PCM: channel mapping API implementation

This patch implements the basic data types for the standard channel
mapping API handling.

- The definitions of the channel positions and the new TLV types are
  added in sound/asound.h and sound/tlv.h, so that they can be
  referred from user-space.

- Introduced a new helper function snd_pcm_add_chmap_ctls() to create
  control elements representing the channel maps for each PCM
  (sub)stream.

- Some standard pre-defined channel maps are provided for
  convenience.

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

sound/core/pcm.c

@@ -1105,6 +1105,10 @@ static int snd_pcm_dev_disconnect(struct snd_device *device)
 			break;
 		}
 		snd_unregister_device(devtype, pcm->card, pcm->device);
+		if (pcm->streams[cidx].chmap_kctl) {
+			snd_ctl_remove(pcm->card, pcm->streams[cidx].chmap_kctl);
+			pcm->streams[cidx].chmap_kctl = NULL;
+		}
 	}
  unlock:
 	mutex_unlock(&register_mutex);