dt-bindings: i2c: nomadik: Add power domain to binding

The power domain is used in the example and in the device trees
for this IP block. Add it.
Reported-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Documentation/devicetree/bindings/i2c/st,nomadik-i2c.yaml

@@ -60,6 +60,9 @@ properties:
           - const: i2cclk
           - const: apb_pclk
 
+  power-domains:
+    maxItems: 1
+
   resets:
     maxItems: 1