avcodec/clearvideo: fix invalid shift in tile size check

Fixes: left shift of 1 by 31 places cannot be represented in type 'int'
Fixes: 15631/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_CLEARVIDEO_fuzzer-5690110605000704

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

libavcodec/clearvideo.c

@@ -665,7 +665,7 @@ static av_cold int clv_decode_init(AVCodecContext *avctx)
     }
 
     c->tile_shift = av_log2(c->tile_size);
-    if (1 << c->tile_shift != c->tile_size) {
+    if (1U << c->tile_shift != c->tile_size) {
         av_log(avctx, AV_LOG_ERROR, "Tile size: %d, is not power of 2.\n", c->tile_size);
         return AVERROR_INVALIDDATA;
     }