avfilter/af_amix: use ff_all_channel_counts() instead of ff_all_channel_layouts()

Adds support for filtering frames with unknown channel layouts.

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/af_amix.c

@@ -521,7 +521,7 @@ static int query_formats(AVFilterContext *ctx)
     AVFilterChannelLayouts *layouts;
     int ret;
 
-    layouts = ff_all_channel_layouts();
+    layouts = ff_all_channel_counts();
     if (!layouts) {
         ret = AVERROR(ENOMEM);
         goto fail;