QSV: decavcodec cleanup, part 1.
QSV: decavcodec cleanup, part 2.
QSV: remove check for impossible condition.

pv->job->qsv == NULL && pv->video_codec_opened >  0 && !strstr(codec, "qsv"):
Can't happen; if the second and third conditions are met, pv->job->qsv is never NULL.

pv->job->qsv == NULL && pv->video_codec_opened <= 0 && !strstr(codec, "qsv")
Pointless check; if the second condition is met, codec is "" so the third condition is not met and is_encode_only is true.