xen/timer: Missing IRQF_NO_SUSPEND in timer code broke suspend.

The patches missed an indirect use of IRQF_NO_SUSPEND pulled in via
IRQF_TIMER. The following patch fixes the issue.

With this fixlet PV guest migration works just fine. I also booted the
entire series as a dom0 kernel and it appeared fine.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>