dt-bindings: clock: qcom,gcc-sc8280xp: document power domain

GCC clock controller is supplied by CX power domain:

sc8280xp-crd.dtb: clock-controller@100000: Unevaluated properties are not allowed ('power-domains' was unexpected)

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Bjorn Andersson <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/clock/qcom,gcc-sc8280xp.yaml

···
       - description: First EMAC controller reference clock
       - description: Second EMAC controller reference clock
 
+  power-domains:
+    items:
+      - description: CX domain
+
   protected-clocks:
     maxItems: 389
 
···
 examples:
   - |
     #include <dt-bindings/clock/qcom,rpmh.h>
+    #include <dt-bindings/power/qcom-rpmpd.h>
+
     clock-controller@100000 {
       compatible = "qcom,gcc-sc8280xp";
       reg = <0x00100000 0x1f0000>;
···
                <&pcie4_lane>,
                <&rxc0_ref_clk>,
                <&rxc1_ref_clk>;
+      power-domains = <&rpmhpd SC8280XP_CX>;
 
       #clock-cells = <1>;
       #reset-cells = <1>;