ARM: S3C24XX: Move irq syscore-ops to irq-pm

With this the definition of s3c24xx_irq_syscore_ops can also move to
common.h from plat/pm.h and the definitions of s3c24xx_irq_suspend
and s3c24xx_irq_resume are also not necessary anymore in plat/pm.h

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>