avcodec/utils: apply the same alignment to YUV410 as we do to YUV420 for snow

The snow encoder uses block based motion estimation which can read out of array if
insufficient alignment is used

It may be better to only apply this for the encoder, as it would safe a few bytes of memory
for the decoder. Until then, this fixes the issue in a simple way.

Fixes: out of array access
Fixes: 68963/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SNOW_fuzzer-4979988435632128
Fixes: 68969/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SNOW_fuzzer-6239933667803136.fuzz
Fixed: 70497/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SNOW_fuzzer-5751882631413760

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

libavcodec/utils.c

@@ -259,6 +259,9 @@ void avcodec_align_dimensions2(AVCodecContext *s, int *width, int *height,
         if (s->codec_id == AV_CODEC_ID_SVQ1) {
             w_align = 64;
             h_align = 64;
+        } else if (s->codec_id == AV_CODEC_ID_SNOW) {
+            w_align = 16;
+            h_align = 16;
         }
         break;
     case AV_PIX_FMT_RGB555: