ARM: dts: Fix igepv5 power button GPIO direction

It should be GPIO_ACTIVE_LOW instead of GPIO_ACTIVE_HIGH as
pointed out by Pau Pajuel <ppajuel@gmail.com>.

Cc: Agustí Fontquerni i Gorchs <afontquerni@iseebcn.com>
Cc: Enric Balletbo Serra <eballetbo@gmail.com>
Cc: Javier Martinez Canillas <javier@osg.samsung.com>
Cc: Pau Pajuel <ppajuel@gmail.com>
Fixes: b118c6a6

 ("ARM: dts: Add power button support for igepv5")
Signed-off-by: Tony Lindgren <tony@atomide.com>