ASoC: SDCA: Minor selected/detected mode control fixups

Make the names a slightly better match for the specification and add
some constants for the values rather than hard coding.

Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.dev>
Link: https://patch.msgid.link/20250624122844.2761627-5-ckeepax@opensource.cirrus.com


Signed-off-by: Mark Brown <broonie@kernel.org>