Since D3D11 was introduced for QSV in FFmpeg 5.0, there is an implied
API/ABI change for user-supplied frames [1], hence update the
description for AV_PIX_FMT_QSV.
[1] https://ffmpeg.org/pipermail/ffmpeg-devel/2021-December/290444.html
Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>