ARM: S5PV310: Add L2 cache init function in cpu.c

This patch adds L2 cache initialization code in cpu.c of ARCH_S5PV310.
It includes TAG and Data latency, Prefetch, and Power configurations.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Changhwan Youn <chaos.youn@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>