avcodec/lpc: Fix lpc_apply_welch_window_c() for odd len

Also removes assert
this fixes an assertion failure on non-x86
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/lpc.c

@@ -37,13 +37,19 @@ static void lpc_apply_welch_window_c(const int32_t *data, int len,
     double w;
     double c;
 
-    /* The optimization in commit fa4ed8c does not support odd len.
-     * If someone wants odd len extend that change. */
-    av_assert2(!(len & 1));
-
     n2 = (len >> 1);
     c = 2.0 / (len - 1.0);
 
+    if (len & 1) {
+        for(i=0; i<n2; i++) {
+            w = c - i - 1.0;
+            w = 1.0 - (w * w);
+            w_data[i] = data[i] * w;
+            w_data[len-1-i] = data[len-1-i] * w;
+        }
+        return;
+    }
+
     w_data+=n2;
       data+=n2;
     for(i=0; i<n2; i++) {