ARM: S5PV210: remove useless ifdef in common.h

The mach-s5pv210 should be complied with selecting CPU_S5PV210,
so the 'ifdef' in common.h is not required.

Reported-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>