Tracker: use set_dataflash() for static logging

AntennaTracker/system.cpp

@@ -66,6 +66,8 @@ void Tracker::init_tracker()
     log_init();
 #endif
 
+    GCS_MAVLINK::set_dataflash(&DataFlash);
+
     if (g.compass_enabled==true) {
         if (!compass.init() || !compass.read()) {
             hal.console->println("Compass initialisation failed!");