drivers/irqchip: Replace pr_warning by pr_warn

Update the last pr_warning callsite in drivers/irqchip.

Signed-off-by: Wang Long <long.wanglong@huawei.com>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: <wanglong@laoqinren.net>
Cc: <peifeiyue@huawei.com>
Cc: <jason@lakedaemon.net>
Cc: <kgene@kernel.org>
Cc: <k.kozlowski@samsung.com>
Link: http://lkml.kernel.org/r/1437466261-147373-1-git-send-email-long.wanglong@huawei.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>