avformat/sdsdec: Use av_rescale() to avoid intermediate overflow in duration calculation

Fixes: signed integer overflow: 72128794995445727 * 240 cannot be represented in type 'long'
Fixes: 50993/clusterfuzz-testcase-minimized-ffmpeg_dem_SDS_fuzzer-6628185583779840

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

libavformat/sdsdec.c

@@ -112,7 +112,7 @@ static int sds_read_header(AVFormatContext *ctx)
     st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
     st->codecpar->ch_layout.nb_channels = 1;
     st->codecpar->sample_rate = sample_period ? 1000000000 / sample_period : 16000;
-    st->duration = (avio_size(pb) - 21) / (127) * s->size / 4;
+    st->duration = av_rescale((avio_size(pb) - 21) / 127,  s->size, 4);
 
     avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);