powerpc/mpic: add irq_set_wake support

Add irq_set_wake support. Just add IRQF_NO_SUSPEND to desc->action->flag.
So the wake up interrupt will not be disable in suspend_device_irqs.

Signed-off-by: Wang Dongsheng <dongsheng.wang@freescale.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>