GCS_MAVLink: add GNSS to extended_status data stream

Author: peterbarker

libraries/GCS_MAVLink/GCS_MAVLink_Parameters.cpp

@@ -239,6 +239,9 @@ static const ap_message STREAM_EXTENDED_STATUS_msgs[] = {
 #endif
 #if AP_GPS_GPS2_RTK_SENDING_ENABLED
     MSG_GPS2_RTK,
+#endif
+#if AP_GPS_ENABLED
+    MSG_GNSS,
 #endif
     MSG_NAV_CONTROLLER_OUTPUT,
 #if AP_FENCE_ENABLED