speaker-test: Fix chmapped channel selection without specified chmap

speaker-test: Fix chmapped channel selection without specified chmap

The channel selection currently does not work properly when there is a
driver-provided non-ALSA-traditional channel map but no manual channel
map was explicitely requested with "-m".

For example, the CEA/HDMI 8ch map is FL,FR,RLC,RRC,FC,LFE,RL,RR. Note
that it is otherwise the same as the traditional ALSA channel map,
except that the traditional rear speakers are considered
rear-center speakers and the traditional side speakers are considered
rear speakers.

Speaker-test tries to play back channels in this following order:
  0, /* Front Left  */
  4, /* Center      */
  1, /* Front Right */
  7, /* Side Right  */
  3, /* Rear Right  */
  2, /* Rear Left   */
  6, /* Side Left   */
  5, /* LFE         */

When it is the time to play back Side Left/Right, speaker-test tries to
look for SL/SR in the chmap, but doesn't find it, so it just plays back
channels 6/7 (which indeed are the side speakers, or RL/RR in this
channel map - so the correct channels are selected).

When it becomes the time to playback Rear Left/Right, speaker-test again
tries to find RL/RR in the chmap, and this time it does find them in the
chmap positions 6/7.

So the channels 6/7 are tested twice and 2/3 are never tested.

To fix this, define a generic playback order channel_order[] to be used
when the channel map is present (but not user-defined) and generate a
(speaker/playback number => channel number) mapping with the channels
ordered in the following order:
1. regular channels found in channel_order[] in the defined order,
2. channels not found in channel_order[] ordered by channel number.
3. UNKNOWN channels ordered by channel number.
4. NA channels ordered by channel number.
For channels outside the channel map just use their channel numbers (so
they will be last after all of the above).

For example, if the playback device has a fictional default channel map
of FR,FL,UNKNOWN1,FOO,BAR,RR,RL,UNKNOWN2, the playback order will be
FL,FR,RR,RL,FOO,BAR,UNKNOWN1,UNKNOWN2(,any_extra_channels).

When the channel mapping is specified manually, the specified order is
used for playback as before.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
Signed-off-by: Takashi Iwai <tiwai@suse.de>