fixed baro offset calculation

- do not subtract the height sensor offset variable when computing the
baro offset from the local origin. The baro height offset is calculated
when baro is not fused and so the height sensor offset used in that case
is associated to another sensor and has nothing to do with the baro.

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

EKF/control.cpp

@@ -766,7 +766,7 @@ void Ekf::controlHeightFusion()
 		local_time_step = math::constrain(local_time_step, 0.0f, 1.0f);
 
 		// apply a 10 second first order low pass filter to baro offset
-		float offset_rate_correction =  0.1f * (_baro_sample_delayed.hgt - _hgt_sensor_offset + _state.pos(
+		float offset_rate_correction =  0.1f * (_baro_sample_delayed.hgt + _state.pos(
 				2) - _baro_hgt_offset);
 		_baro_hgt_offset += local_time_step * math::constrain(offset_rate_correction, -0.1f, 0.1f);
 	}