Avoiding overflow in cross correlation in NetEq.

BUG=

Review-Url: https://codereview.webrtc.org/1908623002
Cr-Commit-Position: refs/heads/master@{#12538}

webrtc/modules/audio_coding/neteq/expand.h

@@ -120,12 +120,10 @@ class Expand {
 
   // Calculate the auto-correlation of |input|, with length |input_length|
   // samples. The correlation is calculated from a downsampled version of
-  // |input|, and is written to |output|. The scale factor is written to
-  // |output_scale|.
+  // |input|, and is written to |output|.
   void Correlation(const int16_t* input,
                    size_t input_length,
-                   int16_t* output,
-                   int* output_scale) const;
+                   int16_t* output) const;
 
   void UpdateLagIndex();