ARM: dts: Fix apparent GPIO typo in exynos5250-arndale

The GPIO flag 2 has no constant assigned, so this was probably
active-low.

Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Andreas Faerber <afaerber@suse.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>