ARM: shmobile: lager: 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.

Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Tested-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>