ekf2: pass gpsSample around where required

- this minimizes potential misuse accessing _gps_sample_delayed and
makes the dependency clear

src/modules/ekf2/EKF/height_control.cpp

@@ -44,7 +44,7 @@ void Ekf::controlHeightFusion()
 	updateGroundEffect();
 
 	controlBaroHeightFusion();
-	controlGnssHeightFusion();
+	controlGnssHeightFusion(_gps_sample_delayed);
 	controlRangeHeightFusion();
 	controlEvHeightFusion();