AV_PIX_FMT_VUYX is used for 8bit 4:4:4 content in FFmpeg VAAPI, so
AV_PIX_FMT_VUYX should be used for 8bit 4:4:4 content in FFmpeg QSV too
because QSV is based on VAAPI on Linux. However the SDK only declares
support for AYUV and does nothing with the alpha, so this commit fudged
a mapping between AV_PIX_FMT_VUYX and MFX_FOURCC_AYUV.
Reviewed-by: Philip Langdale <philipl@overt.org>
Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>