avcodec/loco: Limit lossy parameter so it is sane and does not overflow

Fixes: 15248/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_LOCO_fuzzer-5087440458481664
Fixes: signed integer overflow: 3 + 2147483647 cannot be represented in type 'int'

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

libavcodec/loco.c

@@ -295,6 +295,11 @@ static av_cold int decode_init(AVCodecContext *avctx)
         avpriv_request_sample(avctx, "LOCO codec version %i", version);
     }
 
+    if (l->lossy > 65536U) {
+        av_log(avctx, AV_LOG_ERROR, "lossy %i is too large\n", l->lossy);
+        return AVERROR_INVALIDDATA;
+    }
+
     l->mode = AV_RL32(avctx->extradata + 4);
     switch (l->mode) {
     case LOCO_CYUY2: