ARM: S3C24XX: Fix s3c24xx build errors if !CONFIG_PM

v2:
- register_syscore_ops(&s3c24xx_irq_syscore_ops) does not need to be
  conditionally compiled out, it is already optimized out on !CONFIG_PM
- fix also s3c2412 and s3c2416 affected by the same build issue

v1:
s3c2440.c fails to build if !CONFIG_PM because in such case
s3c2410_pm_syscore_ops is not defined. Same error should happen also
in s3c2410.c and s3c2442.c

Signed-off-by: Domenico Andreoli <cavokz@gmail.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>