Разобрался:
func makeFullScreen(){
NSLayoutConstraint.activate([
sceneView.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 0),
sceneView.rightAnchor.constraint(equalTo: self.view.rightAnchor, constant: 0),
sceneView.leftAnchor.constraint(equalTo: self.view.leftAnchor, constant: 0),
sceneView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: 0),
])
}