ARM: S5PV310: Remove L2 cache init in machine

Basically, need L2 cache initialize function in ARCH_S5PV310. So it would
be better to move it into ARCH_S5PV310 common part. This patch removes L2
cache initialization code at the each board file.

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>