ASoC: google: dt-bindings: modify machine bindings for two MICs case

Add a property "dmic-gpios" for switching between two MICs.

Signed-off-by: Ajye Huang <ajye_huang@compal.corp-partner.google.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201106061433.1483129-2-ajye_huang@compal.corp-partner.google.com


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