dt-bindings: power: gpcv2: correct patternProperties

i.MX8MQ has pgc 'power-domain@a', so correct patternProperties
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220923075427.985504-1-peng.fan@oss.nxp.comSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/power/fsl,imx-gpcv2.yaml

@@ -53,7 +53,7 @@ properties:
         const: 0
 
     patternProperties:
-      "power-domain@[0-9]$":
+      "power-domain@[0-9a-f]+$":
         type: object
         additionalProperties: false