avformat/iamf_parse: Check for negative sample sizes

Fixes: index -2 out of bounds for type 'const enum AVCodecID [3]'
Fixes: 69866/clusterfuzz-testcase-minimized-ffmpeg_dem_IAMF_fuzzer-4971166119821312

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 9b9e02f2ff)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/iamf_parse.c

@@ -152,7 +152,7 @@ static int ipcm_decoder_config(IAMFCodecConfig *codec_config,
     };
     int sample_format = avio_r8(pb); // 0 = BE, 1 = LE
     int sample_size = (avio_r8(pb) / 8 - 2); // 16, 24, 32
-    if (sample_format > 1 || sample_size > 2 || codec_config->audio_roll_distance)
+    if (sample_format > 1 || sample_size > 2U || codec_config->audio_roll_distance)
         return AVERROR_INVALIDDATA;
 
     codec_config->codec_id = sample_fmt[sample_format][sample_size];