dt-bindings: gpu: samsung-rotator: Add missing properties

Add common properties appearing in DTSes (iommus, power-domains) to fix
dtbs_check warnings like:

  arch/arm/boot/dts/exynos4210-i9100.dt.yaml: rotator@12810000:
    'iommus', 'power-domains' do not match any of the regexes: 'pinctrl-[0-9]+'
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200923150339.12497-1-krzk@kernel.orgSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/gpu/samsung-rotator.yaml

@@ -22,6 +22,12 @@ properties:
   interrupts:
     maxItems: 1
 
+  iommus:
+    maxItems: 1
+
+  power-domains:
+    maxItems: 1
+
   clocks:
     maxItems: 1