irqchip: sunxi-nmi: Fix off-by-one error in irq iterator

Fixes: 6058bb36

 'ARM: sun7i/sun6i: irqchip: Add irqchip driver for NMI controller'
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Carlo Caione <carlo@caione.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1433684009.9134.1.camel@ingics.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>