ARM: S5PC100: Move External Interrupt definitions

This patch moves external interrupt definitions from mach/gpio.h
to mach/regs-gpio.h for consistency with S5PV210.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>