bug(tail): `/dev/mem` skips the other arguments

Hi, uutils mainteners

we confirmed that the -f `/dev/mem` skips all other files, and exits

```css
relunsec@relunsec:~/software/coreutils/target/debug$ sudo ./tail -f /dev/mem a
==> /dev/mem <==
tail: Permission denied
relunsec@relunsec:~/software/coreutils/target/debug$ sudo gnutail -f /dev/mem a
==> /dev/mem <==
gnutail: error reading '/dev/mem': Operation not permitted

==> a <==
^C
```