QSV frame priority bits are not being marked correctly; their priorities
are always marked either low or disposable, whereas I-frames should be
marked as highest (3), P-frames should be marked as high (2), and other
frames should be marked as either low or disposable. This helps ensure
that the correct frames are dropped when frames need to be dropped.
When using per-encoder rescaling, QSV would overwrite the current
encoder scale value in the get_video_info callback with the base video
width/height instead of using the current encoder width/height.
