[ARM] 3783/1: S3C2412: fix IRQ_EINT0 to IRQ_EINT3 handling

Patch from Ben Dooks

The IRQ_EINT0 through IRQ_EINT3 handling has changed
on the S3C2412 from the previous SoCs in the range,
and thus we need to add code to handle this.

The changes come about due to these IRQs being
displayed in two different registers, and needing to
be acked and masked in both.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>