[telemetry] reverse order of messages to send periodicaly

This way, messages that are send at low frequency have less chance to be
discarded if the uart buffer is filled by too many messages at the same
time. Higher frequency messages are most likely to find an empty slot.

sw/tools/gen_periodic.ml

@@ -92,7 +92,7 @@ let output_modes = fun out_h process_name modes freq modules ->
           left ();
           lprintf out_h "}\n"
         )
-        messages;
+        (List.rev messages);
       left ();
       lprintf out_h "}\n")
     modes