ASoC: cs-amp-lib-test: Add tests for cs_amp_get_vendor_spkid()

ASoC: cs-amp-lib-test: Add tests for cs_amp_get_vendor_spkid()

Add test cases for cs_amp_get_vendor_spkid() for the Lenovo speaker ID
UEFI variable.

This is a simple set of cases:
- EFI variable is not found
- EFI variable size is larger than the expect 1 byte
- EFI variable has invalid value 0
- Lenovo UEFI variable valid values are interpreted correctly
- HP UEFI variable valid values are interpreted correctly

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Message-ID: <20250909113039.922065-5-rf@opensource.cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>