[generators] gen_periodic: one var j for all modes

no need for a separate one for each mode, also takes care of unused var warnings when a mode is empty...

sw/tools/generators/gen_periodic.ml

@@ -40,6 +40,9 @@ let lprintf = fun c f ->
 let output_modes = fun out_h process_name modes freq modules ->
   let min_period = 1./.float freq in
   let max_period = 65536. /. float freq in
+
+  lprintf out_h "uint8_t j;\n";
+
   (** For each mode in this process *)
   List.iter
     (fun mode ->
@@ -65,8 +68,6 @@ let output_modes = fun out_h process_name modes freq modules ->
         lprintf out_h "static %s %s = 0; %s++; if (%s>=%d) %s=0;\n" _type v v v m v;
       ) modulos;
 
-      lprintf out_h "uint8_t j;\n";
-
       (** For each message in this mode *)
       let messages = List.sort (fun (_,p) (_,p') -> compare p p') messages in
       let i = ref 0 in (** Basic balancing:1 message every 10Hz *)