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