AP_Mount: pass vector by const reference

libraries/AP_Mount/SoloGimbal.cpp

@@ -373,7 +373,7 @@ Vector3f SoloGimbal::get_ang_vel_dem_body_lock()
     return gimbalRateDemVecBodyLock;
 }
 
-void SoloGimbal::update_target(Vector3f newTarget)
+void SoloGimbal::update_target(const Vector3f &newTarget)
 {
     // Low-pass filter
     _att_target_euler_rad.y = _att_target_euler_rad.y + 0.02f*(newTarget.y - _att_target_euler_rad.y);

libraries/AP_Mount/SoloGimbal.h

@@ -56,7 +56,7 @@ public:
         AP_AccelCal::register_client(this);
     }
 
-    void    update_target(Vector3f newTarget);
+    void    update_target(const Vector3f &newTarget);
     void    receive_feedback(mavlink_channel_t chan, const mavlink_message_t *msg);
 
     void update_fast();