ASoC: cs35l56: Some KUnit testing of cs35l56_get_speaker_id()

ASoC: cs35l56: Some KUnit testing of cs35l56_get_speaker_id()

Add some KUnit tests for cs35l56_get_speaker_id().
These only test the simpler cases of reading the speaker ID from
cs_amp_get_vendor_spkid() or the "cirrus,speaker-id" property.

The untested case is reading it from GPIOs, which would require
a dummy implementation of a GPIO driver.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://patch.msgid.link/20260304162402.1714759-3-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>