libvpx: Pull from upstream

source/libvpx/vp9/encoder/vp9_psnr.c

-/*
- *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#include <math.h>
-
-#include "vpx_scale/yv12config.h"
-
-#define MAX_PSNR 100
-
-double vp9_mse2psnr(double samples, double peak, double mse) {
-  double psnr;
-
-  if (mse > 0.0)
-    psnr = 10.0 * log10(peak * peak * samples / mse);
-  else
-    psnr = MAX_PSNR;  // Limit to prevent / 0
-
-  if (psnr > MAX_PSNR)
-    psnr = MAX_PSNR;
-
-  return psnr;
-}