ASoC: dt-bindings: fsl-sai: Add power-domains

Some SoC like i.MX8QXP use a power-domain for this IP, so add it to the
supported properties.
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://msgid.link/r/20231219122957.3358149-1-alexander.stein@ew.tq-group.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/fsl,sai.yaml

@@ -76,6 +76,9 @@ properties:
           - const: pll11k
         minItems: 4
 
+  power-domains:
+    maxItems: 1
+
   dmas:
     items:
       - description: DMA controller phandle and request line for RX