irqchip/eznps: Acknowledge NPS_IPI before calling the handler

irqchip/eznps: Acknowledge NPS_IPI before calling the handler

IPI_IRQ (also TIMER0_IRQ) should be acked before the action->handler is called
in handle_percpu_devid_irq.

The IPI irq is edge sensitive and we might miss an IPI interrupt if it is
triggered again while the handler runs.

Fixes: 44df427c894a ("irqchip: add nps Internal and external irqchips")
Signed-off-by: Noam Camus <noamca@mellanox.com>
Cc: marc.zyngier@arm.com
Cc: jason@lakedaemon.net
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1476364532-12634-1-git-send-email-noamca@mellanox.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>