dt-bindings: gpu: arm,mali-utgard: Correct Maxime's email

Update the address of Maxime Ripard as one in @free-electrons.com does
not work.

Cc: Maxime Ripard <mripard@kernel.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200903191438.12781-3-krzk@kernel.orgSigned-off-by: Rob Herring <robh@kernel.org>

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

@@ -8,7 +8,7 @@ title: ARM Mali Utgard GPU
 
 maintainers:
   - Rob Herring <robh@kernel.org>
-  - Maxime Ripard <maxime.ripard@free-electrons.com>
+  - Maxime Ripard <mripard@kernel.org>
   - Heiko Stuebner <heiko@sntech.de>
 
 properties: