FixedWingAttitudeControl: use trim airspeed if airspeed is disabled

- prior to this fix the fw attiude controller used airspeed to scale control
surfaces even though airspeed was disabled

Signed-off-by: Roman <bapstroman@gmail.com>

src/modules/fw_att_control/FixedwingAttitudeControl.hpp

@@ -202,6 +202,7 @@ private:
 		int32_t vtol_type;					/**< VTOL type: 0 = tailsitter, 1 = tiltrotor */
 
 		int32_t bat_scale_en;			/**< Battery scaling enabled */
+		bool airspeed_disabled;
 
 	} _parameters{};			/**< local copies of interesting parameters */
 
@@ -269,6 +270,7 @@ private:
 		param_t vtol_type;
 
 		param_t bat_scale_en;
+		param_t airspeed_mode;
 
 	} _parameter_handles{};		/**< handles for interesting parameters */