kselftest: alsa: Use private alsa-lib configuration in mixer test

As mentined by Takashi Sakamoto, the system-wide alsa-lib configuration
may override the standard device declarations. This patch use the private
alsa-lib configuration to set the predictable environment.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20211208095209.1772296-1-perex@perex.cz


[Restructure version test to keep the preprocessor happy -- broonie]
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20211210185410.740009-4-broonie@kernel.org


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