qapi: Eliminate QCO_NO_OPTIONS for a slight simplification

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-Id: <20211028102520.747396-4-armbru@redhat.com>

scripts/qapi/commands.py

@@ -229,15 +229,12 @@ def gen_register_command(name: str,
     if coroutine:
         options += ['QCO_COROUTINE']
 
-    if not options:
-        options = ['QCO_NO_OPTIONS']
-
     ret = mcgen('''
     qmp_register_command(cmds, "%(name)s",
                          qmp_marshal_%(c_name)s, %(opts)s);
 ''',
                 name=name, c_name=c_name(name),
-                opts=" | ".join(options))
+                opts=' | '.join(options) or 0)
     return ret