avcodec/lpc: account for odd len values

Reviewed-by: Rémi Denis-Courmont <remi@remlab.net>
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/lpc.c

@@ -120,9 +120,8 @@ static void lpc_compute_autocorr_c(const double *data, ptrdiff_t len, int lag,
 
     if(j==lag){
         double sum = 1.0;
-        for(i=j-1; i<len; i+=2){
-            sum += data[i  ] * data[i-j  ]
-                 + data[i+1] * data[i-j+1];
+        for(i=j-1; i<len; i++){
+            sum += data[i] * data[i-j];
         }
         autoc[j] = sum;
     }