hings set up and ready for line_open().

We need tty_driver available to call tty_{un,}register_device(), so we just
stash a reference to it into struct line_driver.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>
6ª
†“'x