irqchip/atmel-aic: Change return type of aic_common_set_priority()

Priority validation is not necessary because aic_common_irq_domain_xlate()
already handles it. With this removal, return type can be changed to void.

Signed-off-by: Milo Kim <milo.kim@ti.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Ludovic Desroches <ludovic.desroches@atmel.com>
Cc: Nicholas Ferre <nicolas.ferre@atmel.com>
Link: http://lkml.kernel.org/r/1452669592-3401-3-git-send-email-milo.kim@ti.com


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