ASoC: max98090: Enable both DMIC channels also when using mono configuration

According to MAX98090 specification "Digital microphone clock (DMC) is
enabled once both data channels are enabled.". Therefore both digital
microphone data channels must be enabled also when using mono microphone
configuration.

Fix this by moving "DMICL_ENA" and "DMICR_ENA" supply widgets from "DMICL"
and "DMICR" inputs to "DMIC Mux" in order to enable both data channels
whenever there is active mono or stereo digital microphone input path.

Use of "DMICL" and "DMICR" inputs are retained for informative source and in
case the driver would find use for exact digital microphone configuration in
the future.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>