kselftest/alsa: pcm - Add more coverage by default

Add more coverage to our standard test cases:

- 8kHz mono and stereo to verify that the most common mono format is
clocked correctly.
- 44.1kHz stereo to verify that this different clock base is generated
accurately.
- 48kHz 6 channel to verify that 6 channel is clocked correctly.
- 96kHz stereo since that is a common audiophile rate.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221208-alsa-pcm-test-hacks-v4-7-5a152e65b1e1@kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

kselftest/alsa: pcm - Provide descriptions for the default tests

Help people understand what the standard tests are trying to cover by
providing descriptions which both serve as comments in the file and log
messages in the program's output.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221208-alsa-pcm-test-hacks-v4-6-5a152e65b1e1@kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

kselftest/alsa: pcm - move more configuration to configuration files

Obtain all test parameters from the configuration files. The defaults
are defined in the pcm-test.conf file. The test count and parameters
may be variable per specific hardware.

Also, handle alt_formats field now (with the fixes in the format loop).
It replaces the original "automatic" logic which is not so universal.

The code may be further extended to skip various tests based
on the configuration hints, if the exact PCM hardware parameters
are not available for the given hardware.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221208-alsa-pcm-test-hacks-v4-2-5a152e65b1e1@kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>