ARM S3C24XX: Fix compilation of PM code for S3C2416

S3C2416 PM code uses low-level sleep routines from S3C2412 code,
but these routines are compiled only for S3C2412 SoC.

Split S3C2412_PM to two parts: S3C2412_PM, S3C2412_PM_SLEEP and
select last in S3C2416's Kconfig.

Signed-off-by: Yauhen Kharuzhy <jekhor@gmail.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>