dt-bindings: gpu: mali-utgard: add optional supply regulator

Mali GPUs have a separate supplying regulator in a lot of socs,
so describe a mali-supply property. The already described
operating points will likely also need access to this regulator.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/gpu/arm,mali-utgard.txt

@@ -44,6 +44,10 @@ Optional properties:
     Memory region to allocate from, as defined in
     Documentation/devicetree/bindi/reserved-memory/reserved-memory.txt
 
+  - mali-supply:
+    Phandle to regulator for the Mali device, as defined in
+    Documentation/devicetree/bindings/regulator/regulator.txt for details.
+
   - operating-points-v2:
     Operating Points for the GPU, as defined in
     Documentation/devicetree/bindings/opp/opp.txt