Param name is declared as optional, since in code it is an optional
one.
Signed-off-by: NWenchao Xia <wenchaoqemu@gmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>