dt-bindings: clock: qcom,sa8775p-gcc: add the power-domains property

The binding document is missing the power-domains property. Add it and
update the example.

Fixes: 0fff9fa043f9 ("dt-bindings: clock: Add Qualcomm SA8775P GCC")
Signed-off-by: Bartosz Golaszewski <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Bjorn Andersson <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/clock/qcom,sa8775p-gcc.yaml

···
   protected-clocks:
     maxItems: 240
 
+  power-domains:
+    maxItems: 1
+
 required:
   - compatible
   - clocks
···
 examples:
   - |
     #include <dt-bindings/clock/qcom,rpmh.h>
+    #include <dt-bindings/power/qcom-rpmpd.h>
 
     gcc: clock-controller@100000 {
         compatible = "qcom,sa8775p-gcc";
···
                  <&pcie_phy_pipe_clk>,
                  <&rxc0_ref_clk>,
                  <&rxc1_ref_clk>;
+        power-domains = <&rpmhpd SA8775P_CX>;
 
         #clock-cells = <1>;
         #reset-cells = <1>;