CPU_SAVE_VERSION was undefined, so "cpu_common" VMState and
cpu_{save,load}() were not registered. They were no-ops.
Therefore there is no backwards compatibility to keep, so we can mark
S390CPU as unmigratable at device level.
Signed-off-by: Andreas Färber <afaerber@suse.de>
Acked-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
c7396bbb25