ARM: EXYNOS: initial board support for exynos5260 SoC

This patch add basic arch side support for exynos5260 SoC.
Note that this is required to enable build for clock driver.

Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
Signed-off-by: Rahul Sharma <rahul.sharma@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>