ARM: SAMSUNG: Remove static of S5P SoCs sysclass

This patch removes static of s5p6440_sysclass, s5p6442_sysclass,
and s5pv210_sysclass for defintion as extern.

Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>