TTY: tty3270, add tty install

This has two outcomes:
* we give the TTY layer a tty_port
* we do not find the info structure every time open is called on that
  tty

In this case ->install is the only thing we want to do. We do not need
->open at all. See the tty->count > 1 check.

And since we take a reference in ->install, we need also ->cleanup to
drop the reference to a view.

Final note, see that we leave raw3270_find_view in place. It is
because views are removed even from module_exit.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux390@de.ibm.com
Cc: linux-s390@vger.kernel.org
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>