ASoC: wm8988: Replace usage deprecated MUX/ENUM macros

SND_SOC_DAPM_VALUE_MUX and SOC_DAPM_VALUE_ENUM are deprecated and merely an
alias for SND_SOC_DAPM_MUX and SOC_DAPM_ENUM. Replace the deprecated macros so
we can eventually remove their definition.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>