clk: exynos4: Add additional G2D clocks

Add G2D clocks for Exynos4x12 SoC and sclk_fimg2d required by G2D
IP.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Thomas Abraham <thomas.abraham@linaro.org>
Acked-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>