Plane: use camera singleton to get camera rather than callback

ArduPlane/GCS_Mavlink.cpp

@@ -1610,15 +1610,6 @@ void GCS_MAVLINK_Plane::handle_mission_set_current(AP_Mission &mission, mavlink_
     }
 }
 
-AP_Camera *GCS_MAVLINK_Plane::get_camera() const
-{
-#if CAMERA == ENABLED
-    return &plane.camera;
-#else
-    return nullptr;
-#endif
-}
-
 AP_AdvancedFailsafe *GCS_MAVLINK_Plane::get_advanced_failsafe() const
 {
     return &plane.afs;

ArduPlane/GCS_Mavlink.h

@@ -19,7 +19,6 @@ protected:
     AP_Mission *get_mission() override;
     void handle_mission_set_current(AP_Mission &mission, mavlink_message_t *msg) override;
 
-    AP_Camera *get_camera() const override;
     AP_AdvancedFailsafe *get_advanced_failsafe() const override;
     AP_Rally *get_rally() const override;