ARM: mvebu: fix ReadyNAS 102 Power button GPIO to make it active high

NETGEAR ReadyNAS 102 Power button definition in .dts file flags
associated GPIO active low instead of active high. This results
in reversed events reported by input subsystem (0 returned when
the button is pressed, 1 when released). This patch makes
associated GPIO active high to recover correct behaviour.

Signed-off-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>