avcodec/tta: Limit decoder to 16 channels

libtta 2.3 has a limit of 6 channels, so 16 is substantially above the "official" already

Fixes: OOM
Fixes: 15249/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TTA_fuzzer-5643988125614080

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/tta.c

@@ -163,7 +163,7 @@ static av_cold int tta_decode_init(AVCodecContext * avctx)
         s->data_length = get_bits_long(&gb, 32);
         skip_bits_long(&gb, 32); // CRC32 of header
 
-        if (s->channels == 0) {
+        if (s->channels == 0 || s->channels > 16) {
             av_log(avctx, AV_LOG_ERROR, "Invalid number of channels\n");
             return AVERROR_INVALIDDATA;
         } else if (avctx->sample_rate == 0) {