Use av_fast_malloc instead of av_fast_realloc.

Avoids a memleak, is less code and might be faster.

libavcodec/svq3.c

@@ -949,7 +949,7 @@ static int svq3_decode_frame(AVCodecContext *avctx,
     s->mb_x = s->mb_y = h->mb_xy = 0;
 
     if (svq3->watermark_key) {
-        svq3->buf = av_fast_realloc(svq3->buf, &svq3->buf_size,
+        av_fast_malloc(&svq3->buf, &svq3->buf_size,
                        buf_size+FF_INPUT_BUFFER_PADDING_SIZE);
         if (!svq3->buf)
             return AVERROR(ENOMEM);