ffmpeg: add OPT_INPUT to -guess_layout_max.

ffmpeg_opt.c

@@ -2722,7 +2722,7 @@ const OptionDef options[] = {
         "set channel layout", "layout" },
     { "af",             OPT_AUDIO | HAS_ARG  | OPT_PERFILE | OPT_OUTPUT,           { .func_arg = opt_audio_filters },
         "set audio filters", "filter_graph" },
-    { "guess_layout_max", OPT_AUDIO | HAS_ARG | OPT_INT | OPT_SPEC | OPT_EXPERT,   { .off = OFFSET(guess_layout_max) },
+    { "guess_layout_max", OPT_AUDIO | HAS_ARG | OPT_INT | OPT_SPEC | OPT_EXPERT | OPT_INPUT, { .off = OFFSET(guess_layout_max) },
       "set the maximum number of channels to try to guess the channel layout" },
 
     /* subtitle options */