All callbacks FOO_query_hotpluggable_cpus() are practically
the same except of setting vcpus_count to different values.
Convert them to a generic machine_query_hotpluggable_cpus()
callback by moving vcpus_count initialization to per machine
specific callback possible_cpu_arch_ids().
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>