g729dec: initialize bit reader with the correct buffer size

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/g729dec.c

@@ -436,7 +436,7 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
         frame_erasure |= buf[i];
     frame_erasure = !frame_erasure;
 
-    init_get_bits(&gb, buf, buf_size);
+    init_get_bits(&gb, buf, 8*buf_size);
 
     ma_predictor     = get_bits(&gb, 1);
     quantizer_1st    = get_bits(&gb, VQ_1ST_BITS);