numa: fix missing '-numa cpu' in '-help' output

numa: fix missing '-numa cpu' in '-help' output

commit 419fcdec3c (numa: add '-numa cpu,...' option for property based node mapping)
added '-numa cpu' option but forgot to update appropriate section for '--help'.
Add '-numa cpu' description to '-help' output

Reported-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <1511880838-56509-1-git-send-email-imammedo@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>