ARM: dts: Remove unneeded GPIO include in exynos4412-odroidu3

The <dt-bindings/gpio/gpio.h> header is already included in the
exynos4412-odroid-common DTSI so there's no need to do it again
in the DTS file.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>