avformat/mov: Disallow more than one meta box for AVIF

This is not allowed per the spec.

Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
Reviewed-by: Vittorio Giovara <vittorio.giovara@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mov.c

@@ -4903,6 +4903,8 @@ static int avif_add_stream(MOVContext *c, int item_id)
 {
     MOVStreamContext *sc;
     AVStream *st;
+    if (c->fc->nb_streams)
+        return AVERROR_INVALIDDATA;
     int item_index = -1;
     for (int i = 0; i < c->avif_info_size; i++)
         if (c->avif_info[i].item_id == item_id) {