Sub: better check and text message for baro calibration failure

ArduSub/GCS_Mavlink.cpp

@@ -872,7 +872,7 @@ void GCS_MAVLINK_Sub::handle_change_alt_request(AP_Mission::Mission_Command &cmd
 
 MAV_RESULT GCS_MAVLINK_Sub::_handle_command_preflight_calibration_baro()
 {
-    if (!sub.sensor_health.depth) {
+    if (!sub.control_check_barometer()) {
         return MAV_RESULT_FAILED;
     }