AP_SpdHgtControl: update for changed API

libraries/AP_SpdHgtControl/AP_SpdHgtControl.h

@@ -59,9 +59,6 @@ public:
 	// Rate of change of velocity along X body axis in m/s^2
     virtual float get_VXdot(void)=0;
 	
-	// log data on internal state of the controller. Called at 10Hz
-	virtual void log_data(DataFlash_Class &dataflash, uint8_t msgid) = 0;
-
 	// return current target airspeed
 	virtual float get_target_airspeed(void) const = 0;