ARM: mvebu: use correct #interrupt-cells instead of #interrupts-cells

The Device Tree information for the GPIO banks of the Armada 370 and
Armada XP SOCs was incorrectly using #interrupts-cells instead of
controller when using GPIO interrupts, since the GPIO bank DT node
wasn't recognized as a valid interrupt controller by the OF code.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>