ARM: S3C24XX: modify s3c2416 irq init to initialize all irqs

Previously the irq init used s3c24xx_init_irq and an additional
arch_initcall to add the cpu specific irqs.

To be able to simplyfy the irq init later, create a new function
s3c416_init_irq, which then calls s3c24xx_init_irq but also adds
the cpu specific irqs.

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