ASoC: SDCA: Pull the Q7.8 volume helpers out of soc-ops

ASoC: SDCA: Pull the Q7.8 volume helpers out of soc-ops

It is cleaner to keep the SDCA code contained and not update the core
code for things that are unlikely to see reuse outside of SDCA. Move the
Q7.8 volume helpers back into the SDCA core code.

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.dev>
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://patch.msgid.link/20260225140118.402695-5-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>