dt-bindings: clock: mediatek: Add power-domains property

The mt8183-mfgcfg node uses a power domain in its device tree node.
To prevent schema validation warnings, add the optional `power-domains`
property to the binding schema for mediatek syscon clocks.

Fixes: 1781f2c46180 ("arm64: dts: mediatek: mt8183: Add power-domains properity to mfgcfg")
Reviewed-by: AngeloGioacchino Del Regno <[e-mail]>
Signed-off-by: Julien Massot <[e-mail]>
Acked-by: Rob Herring (Arm) <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>

Documentation/devicetree/bindings/clock/mediatek,syscon.yaml

···
           - const: mediatek,mt2701-vdecsys
           - const: syscon
 
+  power-domains:
+    maxItems: 1
+
   reg:
     maxItems: 1
 
···
 required:
   - compatible
   - '#clock-cells'
+
+if:
+  properties:
+    compatible:
+      contains:
+        const: mediatek,mt8183-mfgcfg
+then:
+  properties:
+    power-domains: true
+else:
+  properties:
+    power-domains: false
 
 additionalProperties: false