ARM: dts: Add power domain to G2D device on exynos4210

G2D device and it's SYSMMU belongs to LCD0 power domain on Exynos 4210,
so add missing power-domains property to G2D device node (G2D's SYSMMU is
already bound to LCD0 power domain).

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>