Fix memory leak in FreeRTOS port timer initialization.

Author: h2zero

src/porting/npl/freertos/src/npl_os_freertos.c

@@ -311,8 +311,9 @@ void
 npl_freertos_callout_init(struct ble_npl_callout *co, struct ble_npl_eventq *evq,
                      ble_npl_event_fn *ev_cb, void *ev_arg)
 {
-    memset(co, 0, sizeof(*co));
-    co->handle = xTimerCreate("co", 1, pdFALSE, co, os_callout_timer_cb);
+    if (co->handle == NULL) {
+        co->handle = xTimerCreate("co", 1, pdFALSE, co, os_callout_timer_cb);
+    }
     co->evq = evq;
     ble_npl_event_init(&co->ev, ev_cb, ev_arg);
 }
@@ -321,6 +322,7 @@ npl_freertos_callout_deinit(struct ble_npl_callout *co)
 {
     if (co->handle) {
         xTimerDelete(co->handle, portMAX_DELAY);
+        co->handle = NULL;
     }
 }