ASoC: dt-bindings: rockchip: i2s-tdm: Document power-domains

The binding document is missing the power-domains property. Add it.
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Link: https://lore.kernel.org/r/20230315114806.3819515-7-cristian.ciocaltea@collabora.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/rockchip,i2s-tdm.yaml

@@ -90,6 +90,9 @@ properties:
     $ref: audio-graph-port.yaml#
     unevaluatedProperties: false
 
+  power-domains:
+    maxItems: 1
+
   rockchip,grf:
     $ref: /schemas/types.yaml#/definitions/phandle
     description: