OSV-2020-1161 Heap-buffer-overflow in impeg2_fmt_conv_yuv420p_to_yuv420sp_uv

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=16604 Crash type: Heap-buffer-overflow WRITE 1 Crash state: impeg2fmtconvyuv420ptoyuv420spuv impeg2dformatconvert impeg2ddecpicdatathread...