[ARM] S3C64XX: Correct the EINT IRQ type configuration

Select the correct EINT configuration register when configuring
the external interrupt level/edge type.

Signed-off-by: Matt Hsu <matt_hsu@openmoko.org>
[ben-linux@fluff.org: description improvement]
Signed-off-by: Ben Dooks <ben-linux@fluff.org>