ASoC: codecs: wcd939x: Unify define used for MIC bias VOUT registers

All four microphone bias registers have similar layout: VOUT control
mask is exactly the same.  Use one define, just like older driver
wcd938x is doing, to make the code a bit simpler.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://msgid.link/r/20240523125049.43713-1-krzysztof.kozlowski@linaro.org


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