[ARM] 3347/1: Bugfix for ixp4xx_set_irq_type()

Patch from Mrten Wikstrm

This patch fixes a bug in ixp4xx_set_irq_type() which leads to
GPIO being incorrectly set to both edge triggered for raising
as well as falling edge interrupt types. See the previous
discussion on patch 3312/1.

Signed-off-by: Mrten Wikstrm <marten.wikstrom@passito.se>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>