xen/sched: migrate timers to correct cpus after suspend

xen/sched: migrate timers to correct cpus after suspend

Today all timers are migrated to cpu 0 when the system is being
suspended. They are not migrated back after resuming the system again.

This results (at least) to visible problems with the credit scheduler,
as the timer isn't handled on the cpu it was expected to occur, which
will result in an ASSERT() triggering. Other more subtle problems, like
uninterrupted elongated time slices, are probable. The least effect
will be worse performance on cpu 0 resulting from most scheduling
related timer interrupts happening there after suspend/resume.

Add migrating the scheduling related timers of a specific cpu from cpu
0 back to its original cpu when that cpu has gone up when resuming the
system.

Fixes: 0763cd268789 ("xen/sched: don't disable scheduler on cpus during suspend")
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Dario Faggioli <dfaggioli@suse.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>