ratbagctl: default to list-devices without argv

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

tools/ratbagctl.in

@@ -500,6 +500,8 @@ def make_parser():
     return parser
 
 def main(argv):
+    if not argv:
+        argv = ["list-devices"]
     cmd = make_parser().parse_args(argv)
 
     try: