irqchip/atmel-aic: Fix unbalanced of_node_put() in aic_common_irq_fixup()

aic_common_irq_fixup() is calling twice of_node_put() on the same node
thus leading to an unbalanced refcount on the root node.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reported-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Fixes: b2f579b5 ("irqchip: atmel-aic: Add irq fixup infrastructure")
Cc: <stable@vger.kernel.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>