ARM: SAMSUNG: add G2D to plat-s5p and mach-exynos

G2D is a 2D graphics accelerator engine present in the s5p family
of Samsung SoCs. It is capable of bitblt and raster operations on
images having dimensions of up to 8000x8000.

Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>