ARM: shmobile: koelsch: Fix adv7511 IRQ sensing

The adv7511 IRQ is low level triggered, not falling edge triggered. The
wrong sense configuration results in no interrupt being triggered at
all, breaking hotplug detection. Fix it.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Fixes: 83a0731b ("ARM: shmobile: koelsch: Add DU HDMI output support")
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>