ARM: S5P: Bug fix on external interrupt for S5P SoCs

This patch fixes bug on eint type set function, s5p_irq_eint_set_type().
In the IRQ_TYPE_EDGE_FALLING case, S5P_EXTINT_FALLEDGE is right
instead of S5P_EXTINT_RISEEDGE

Signed-off-by: Boojin Kim <boojin.kim@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>