avformat/mpegts: Limit iterations of get_packet_size()

This is a pathological case where the fuzzer provides only 2 bytes per iteration.

Fixes: Timeout (>30 -> 0.9sec)
Fixes: 26488/clusterfuzz-testcase-minimized-ffmpeg_dem_MPEGTS_fuzzer-5911031077142528

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

libavformat/mpegts.c

@@ -609,8 +609,9 @@ static int get_packet_size(AVFormatContext* s)
     /*init buffer to store stream for probing */
     uint8_t buf[PROBE_PACKET_MAX_BUF] = {0};
     int buf_size = 0;
+    int max_iterations = 16;
 
-    while (buf_size < PROBE_PACKET_MAX_BUF) {
+    while (buf_size < PROBE_PACKET_MAX_BUF && max_iterations--) {
         ret = avio_read_partial(s->pb, buf + buf_size, PROBE_PACKET_MAX_BUF - buf_size);
         if (ret < 0)
             return AVERROR_INVALIDDATA;