dt-bindings: rtc: rtc-sh: Add missing power-domains property

make dtbs_check:

    arch/arm/boot/dts/r7s72100-rskrza1.dt.yaml: rtc@fcff1000: 'power-domains' does not match any of the regexes: 'pinctrl-[0-9]+'

Fix this by documenting the missing power-domains property.
Update the example to match reality.

Fixes: 7ae8b2f5df ("dt-bindings: rtc: rtc-sh: convert bindings to json-schema")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/rtc/renesas,sh-rtc.yaml

@@ -43,6 +43,9 @@ properties:
     items:
       enum: [ fck, rtc_x1, rtc_x3, extal ]
 
+  power-domains:
+    maxItems: 1
+
 required:
   - compatible
   - reg
@@ -50,6 +53,7 @@ required:
   - interrupt-names
   - clocks
   - clock-names
+  - power-domains
 
 additionalProperties: false
 
@@ -68,5 +72,6 @@ examples:
         interrupt-names = "alarm", "period", "carry";
         clocks = <&mstp6_clks R7S72100_CLK_RTC>, <&rtc_x1_clk>,
                  <&rtc_x3_clk>, <&extal_clk>;
+        power-domains = <&cpg_clocks>;
         clock-names = "fck", "rtc_x1", "rtc_x3", "extal";
     };