pinctrl: s3c24xx: use correct header for chained_irq functions

chained_irq_enter and chained_irq_exit moved to a real header
under linux/pinctrl instead of asm/.

Update the pinctrl driver to use the correct header and fix the
build error.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>`
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>