dt-bindings: ufs: cdns,ufshc: Add power-domains

The Cadence UFS controller can be part of power domain (as it is in
example DTS of TI J721e UFS Host Controller Glue), so allow such
property.
Reported-by: Rob Herring <robh@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220427065802.110402-1-krzysztof.kozlowski@linaro.org

Documentation/devicetree/bindings/ufs/cdns,ufshc.yaml

@@ -43,6 +43,9 @@ properties:
       - const: phy_clk
       - const: ref_clk
 
+  power-domains:
+    maxItems: 1
+
   reg:
     maxItems: 1