Update that HMP 'cpu-add' is deprecated in 4.0

Signed-off-by: NKashyap Chamarthy <kchamart@redhat.com>
Message-Id: <20181213124224.31585-3-kchamart@redhat.com>
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>
[ehabkost: revert back to 'cpu-add' spelling]
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>

qemu-deprecated.texi

@@ -113,7 +113,7 @@ replaced by the ``target'' output member.
 The @option{[hub_id name]} parameter tuple of the 'hostfwd_add' and
 'hostfwd_remove' HMP commands has been replaced by @option{netdev_id}.
 
-@subsection cpu-add (since 3.1)
+@subsection cpu-add (since 4.0)
 
 Use ``device_add'' for hotplugging vCPUs instead of ``cpu-add''.  See
 documentation of ``query-hotpluggable-cpus'' for additional details.