avcodec/avpacket: Limit iterations in ff_packet_split_and_drop_side_data()

This avoids scaning beyond what a valid packet can contain
Fixes: Timeout
Fixes: 541/clusterfuzz-testcase-610189291657625

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

libavcodec/avpacket.c

@@ -495,6 +495,8 @@ int ff_packet_split_and_drop_side_data(AVPacket *pkt){
             if (p - pkt->data < size + 5)
                 return 0;
             p-= size+5;
+            if (i > AV_PKT_DATA_NB)
+                return 0;
         }
         pkt->size = p - pkt->data - size;
         av_assert0(pkt->size >= 0);