avcodec/mpegaudio_parser: Consume more than 0 bytes in case of the unsupported mp3adu case

Fixes: Timeout
Fixes: 10966/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MP3ADU_fuzzer-5348695024336896
Fixes: 10969/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MP3ADUFLOAT_fuzzer-5691669402877952

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

libavcodec/mpegaudio_parser.c

@@ -101,7 +101,7 @@ static int mpegaudio_parse(AVCodecParserContext *s1,
                             "MP3ADU full parser");
                         *poutbuf = NULL;
                         *poutbuf_size = 0;
-                        return 0; /* parsers must not return error codes */
+                        return buf_size; /* parsers must not return error codes */
                     }
 
                     break;