selftests: ALSA: remove unused variables

These variables are never referenced in the code, just remove them.

Signed-off-by: Ding Xiang <dingxiang@cmss.chinamobile.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230908081040.197243-1-dingxiang@cmss.chinamobile.com


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