ASoC: codecs: wcd family: cleanups

Merge series from Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>:

Set of simple cleanups from similar issues in all Qualcomm WCD93xx
codecs.

The first patch "ASoC: codecs: wcd-mbhc: Constify passed MBHC reg
fields" is a requirement for few others, but except this they are
independent.