ASoC: sun50i-dmic: dt-bindings: add DT bindings for DMIC controller

DT binding documentation for this new ASoC driver.

Signed-off-by: Ban Tao <fengzheng923@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/1662966333-18000-1-git-send-email-fengzheng923@gmail.com


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