WMA: use DSPContext.butterflies_float

Originally committed as revision 19981 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/wmadec.c

@@ -637,12 +637,7 @@ static int wma_decode_block(WMACodecContext *s)
             s->channel_coded[0] = 1;
         }
 
-        for(i = 0; i < s->block_len; i++) {
+        s->dsp.butterflies_float(s->coefs[0], s->coefs[1], s->block_len);
-            a = s->coefs[0][i];
-            b = s->coefs[1][i];
-            s->coefs[0][i] = a + b;
-            s->coefs[1][i] = a - b;
-        }
     }
 
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