MLP packetizer: small fix

Fix 88d70be0, that was badly cherry-picked.

modules/packetizer/mlp.c

@@ -138,7 +138,7 @@ static int Open( vlc_object_t *p_this )
 
     /* Set output properties */
     p_dec->fmt_out.i_cat = AUDIO_ES;
-    p_dec->fmt_out.i_codec = VLC_FOURCC('t','r','h','d');
+    p_dec->fmt_out.i_codec = p_dec->fmt_in.i_codec;
     p_dec->fmt_out.audio.i_rate = 0;
 
     /* Set callback */