dt-bindings: pinctrl: apple,pinctrl: Add power-domains property

This will bind to the PMGR pwrstate nodes that control power/clock
gating to SoC blocks. The pinctrl driver doesn't do runtime-pm yet, so
initially this will just keep the domain on permanently.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Hector Martin <marcan@marcan.st>

Documentation/devicetree/bindings/pinctrl/apple,pinctrl.yaml

@@ -50,6 +50,9 @@ properties:
   '#interrupt-cells':
     const: 2
 
+  power-domains:
+    maxItems: 1
+
 patternProperties:
   '-pins$':
     type: object