Commit 2b953a5e ("xen: Suspend ticks on all CPUs during suspend")
introduced xen_arch_suspend() routine but did so only for x86, breaking
ARM builds.

We need to add it to ARM as well.
Signed-off-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>
Reported-by: NMichal Suchanek <hramrach@gmail.com>
Tested-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>