avcodec/argo: Move U, fix shift

Fixes: left shift of 255 by 24 places cannot be represented in type 'int'
Fixes: 37249/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ARGO_fuzzer-5754862984888320

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

libavcodec/argo.c

@@ -58,7 +58,7 @@ static int decode_pal8(AVCodecContext *avctx, uint32_t *pal)
         return AVERROR_INVALIDDATA;
 
     for (int i = 0; i < count; i++)
-        pal[start + i] = (0xFF << 24U) | bytestream2_get_be24u(gb);
+        pal[start + i] = (0xFFU << 24) | bytestream2_get_be24u(gb);
 
     return 0;
 }