clk: samsung: exynos5250: Add clocks for G3D

This patch adds the required clocks for ARM Mali IP
in Exynos5250.

Signed-off-by: Arun Kumar K <arun.kk@samsung.com>
[t.figa: Changed clock ID to avoid conflict with CLK_SSS]
Signed-off-by: Tomasz Figa <t.figa@samsung.com>