d/ns: Remove unused file

src/xrt/drivers/north_star/distortion/ns_distortion.c

-// Copyright 2020, Collabora, Ltd.
-// Copyright 2020, Nova King.
-// SPDX-License-Identifier: BSL-1.0
-/*!
- * @file
- * @brief  North Star HMD code.
- * @author Nova King <technobaboo@gmail.com>
- * @author Jakob Bornecrantz <jakob@collabora.com>
- * @ingroup drv_ns
- */
-
-
-#include <math.h>
-#include <stdio.h>
-#include <unistd.h>
-#include <stdlib.h>
-#include <string.h>
-#include <assert.h>
-
-#include "../ns_hmd.h"
-
-void
-ns_display_uv_to_render_uv(struct ns_uv display_uv,
-                           struct ns_uv *render_uv,
-                           struct ns_eye eye)
-{
-	std::map<float, std::map<float, struct ns_uv> >::iterator outerIter;
-}