ARM: EXYNOS: Add 5800 SoC support

Exynos5800 is an octa core SoC which is based on the 5420
platform. This patch adds the basic support for it in the
mach-exynos.

Signed-off-by: Arun Kumar K <arun.kk@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>