xen: Use IRQF_FORCE_RESUME

Mark the IRQF_NO_SUSPEND interrupts IRQF_FORCE_RESUME and remove the extra
walk through the interrupt descriptors.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>