A new option -qsv_params <str> is added, where <str> is a :-separated
list of key=value parameters.

Example:
$ ffmpeg -y -f lavfi -i testsrc -vf "format=nv12" -c:v h264_qsv -qsv_params
"TargetUsage=1:GopPicSize=30:GopRefDist=2:TargetKbps=5000" -f null -
Signed-off-by: Mounika Mandava <mounika.mandava@intel.com>
Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>