lavfi/buffersink: fix abuffersink flag setting issue

abuffersink need to setting AV_OPT_FLAG_AUDIO_PARAM flag.
Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Jun Zhao <mypopydev@gmail.com>

libavfilter/buffersink.c

@@ -320,7 +320,7 @@ static const AVOption buffersink_options[] = {
     { NULL },
 };
 #undef FLAGS
-#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_AUDIO_PARAM
 static const AVOption abuffersink_options[] = {
     { "sample_fmts",     "set the supported sample formats",  OFFSET(sample_fmts),     AV_OPT_TYPE_BINARY, .flags = FLAGS },
     { "sample_rates",    "set the supported sample rates",    OFFSET(sample_rates),    AV_OPT_TYPE_BINARY, .flags = FLAGS },