ASoC: ops: Clarify snd_soc_info_volsw_sx()

Currently snd_soc_info_volsw_sx() is implemented indirectly, wrapping
snd_soc_info_volsw() and modifying the values it sets up rather than
directly setting up the values reported to userspace. This makes it much
harder to follow what the intended behaviour of these controls is. Let's
rewrite the function to be self contained with a clarifying comment at the
top in an effort to help maintainability.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Tested-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20220602092921.3302713-1-broonie@kernel.org


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