ASoC: dt-bindings: mt8173-afe-pcm: Add power domain

The audio subsystem sits under a controllable power domain.

Add it to the binding.

Acked-by: "Rob Herring (Arm)" <robh@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://patch.msgid.link/20250612074901.4023253-3-wenst@chromium.org


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