avcodec/aacdec_fixed: Add FF_CODEC_CAP_INIT_CLEANUP

Fixes: memleaks
Fixes: 16788/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AAC_FIXED_fuzzer-5649873898045440

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

libavcodec/aacdec_fixed.c

@@ -461,7 +461,7 @@ AVCodec ff_aac_fixed_decoder = {
         AV_SAMPLE_FMT_S32P, AV_SAMPLE_FMT_NONE
     },
     .capabilities    = AV_CODEC_CAP_CHANNEL_CONF | AV_CODEC_CAP_DR1,
-    .caps_internal   = FF_CODEC_CAP_INIT_THREADSAFE,
+    .caps_internal   = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,
     .channel_layouts = aac_channel_layout,
     .profiles        = NULL_IF_CONFIG_SMALL(ff_aac_profiles),
     .flush = flush,