ARM: SAMSUNG: Add support for detecting CPU at runtime

The soc_is_[name]() can be used to distinguish cpu at runtime.

This patch was originally from Changhwan Youn <chaos.youn@samsung.com>

Acked-by: Changhwan Youn <chaos.youn@samsung.com>
Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>