avio: redesign ffio_rewind_with_probe_data()

This prevents a double free

Fixes CID718285
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/utils.c

@@ -470,8 +470,7 @@ int av_probe_input_buffer(AVIOContext *pb, AVInputFormat **fmt,
     }
 
     /* rewind. reuse probe buffer to avoid seeking */
-    if ((ret = ffio_rewind_with_probe_data(pb, buf, pd.buf_size)) < 0)
-        av_free(buf);
+    ret = ffio_rewind_with_probe_data(pb, &buf, pd.buf_size);
 
     return ret;
 }