Otherwise, if e.g. "nvdec" didn't work, but "nvdec-copy" did, it would
never try "vdpau", which is actually the next non-copy mode on the
autprobe list. It's really expected that it selects "vdpau". Fix this by
sorting the -copy modes to the end of the final hwdec list.
But we still don't want preferred -copy modes like "nvdec-copy" to be
sorted after fragile non-preferred modes like "cuda", and --hwdec=auto
should prefer "nvdec-copy" over it, so make sure the copying mode does
not get precedence over preferred vs. non-preferred mode.
Also simplify the existing auto_pos sorting condition, and fix the
fallback sort order (although that doesn't matter too much).