avformat/rmdec: use larger intermediate type for audio_framesize * sub_packet_h check

Fixes: signed integer overflow: 65535 * 65535 cannot be represented in type 'int'
Fixes: 31406/clusterfuzz-testcase-minimized-ffmpeg_dem_IVR_fuzzer-5024692843970560

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

libavformat/rmdec.c

@@ -296,7 +296,7 @@ static int rm_read_audio_stream_info(AVFormatContext *s, AVIOContext *pb,
             ast->deint_id == DEINT_ID_GENR ||
             ast->deint_id == DEINT_ID_SIPR) {
             if (st->codecpar->block_align <= 0 ||
-                ast->audio_framesize * sub_packet_h > (unsigned)INT_MAX ||
+                ast->audio_framesize * (uint64_t)sub_packet_h > (unsigned)INT_MAX ||
                 ast->audio_framesize * sub_packet_h < st->codecpar->block_align)
                 return AVERROR_INVALIDDATA;
             if (av_new_packet(&ast->pkt, ast->audio_framesize * sub_packet_h) < 0)