GCS_MAVLink: send SCALED_PRESSURE3 for 3 baros

libraries/GCS_MAVLink/GCS_Common.cpp

@@ -1121,6 +1121,17 @@ void GCS_MAVLINK::send_scaled_pressure(AP_Baro &barometer)
             barometer.get_temperature(1)*100); // 0.01 degrees C        
     }
 #endif
+#if BARO_MAX_INSTANCES > 2
+    if (barometer.num_instances() > 2) {
+        pressure = barometer.get_pressure(2);
+        mavlink_msg_scaled_pressure3_send(
+            chan,
+            now,
+            pressure*0.01f, // hectopascal
+            (pressure - barometer.get_ground_pressure(2))*0.01f, // hectopascal
+            barometer.get_temperature(2)*100); // 0.01 degrees C        
+    }
+#endif
 }
 
 void GCS_MAVLINK::send_sensor_offsets(const AP_InertialSensor &ins, const Compass &compass, AP_Baro &barometer)