mlp_parser: Fix memleak.

ff_combine_frame() is called, which allocates ParseContext->buffer if needed,
so ff_parse_close() must be called to free it.
Patch by jai.

Originally committed as revision 22005 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mlp_parser.c

@@ -293,5 +293,5 @@ AVCodecParser mlp_parser = {
     sizeof(MLPParseContext),
     mlp_init,
     mlp_parse,
-    NULL,
+    ff_parse_close,
 };