ASoC: codecs: wcd-mbhc: Constify passed MBHC reg fields

The wcd-mbhc-v2 helper code/module does not modify passed array of
registry fields, thus it can be made const for code safety.  It will
also allow individual drivers to allocate the array in rodata.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://msgid.link/r/20240612-asoc-wcd9xxx-wide-cleanups-v1-1-0d15885b2a06@linaro.org


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