ARM: dts: exynos: Add GPU/Mali 400 node to Exynos4

Add nodes for GPU (Mali 400) to Exynos4210 and Exynos4412.  Describe the
GPU as much as possible however still few elements are missing:
1. Exynos4210 bus clock is not described in hardware manual therefore
   the IP gate clock was provided,
2. Exynos4412: Not sure what to do with CLK_G3D clock responsible for
   gating entire IP block (it is now being disabled as unused),
3. Regulator supplies on Trats board.

Limited testing on Odroid U3 (Exynos4412).

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>