nr rlc stats: make avg time to tx optional

Introduce the function nr_rlc_activate_avg_time_to_tx() to
activate/deactivate collection of avg time to tx stats (which
may have an impact on realtime processing, so better not compute
them when not needed).

Fix a little bug in time_average_get_average() for when there is not stat.

common/utils/time_stat.c

@@ -61,6 +61,14 @@ void time_average_free(time_average_t *t)
   free(t);
 }
 
+void time_average_reset(time_average_t *t)
+{
+  t->r.head = t->r.maxsize - 1;
+  t->r.tail = 0;
+  t->r.size = 0;
+  t->accumulated_value = 0;
+}
+
 static void remove_old(time_average_t *t, uint64_t time)
 {
   /* remove old events */
@@ -103,6 +111,9 @@ double time_average_get_average(time_average_t *t, uint64_t time)
 {
   remove_old(t, time);
 
+  if (t->r.size == 0)
+    return 0;
+
   return (double)t->accumulated_value / t->r.size;
 }
 

common/utils/time_stat.h

@@ -46,6 +46,7 @@ typedef struct {
 /* 'duration' is in unit microsecond */
 time_average_t *time_average_new(int duration, int initial_size);
 void time_average_free(time_average_t *t);
+void time_average_reset(time_average_t *t);
 
 /* add a value tagged with time 'time' unit microsecond (it also modifies 't',
  * removing all data with time < 'time' - t->duration)