ALSA: hda: cs35l56: Remove unused test stub function

Remove an unused stub function that calls a non-existant function.

This function was accidentally added as part of commit
2144833e

 ("ALSA: hda: cirrus_scodec: Add KUnit test"). It was
a relic of an earlier version of the test that should have been
removed.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Fixes: 2144833e

 ("ALSA: hda: cirrus_scodec: Add KUnit test")
Link: https://msgid.link/r/20240129162737.497-19-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>