TTY: hso, free tty_driver

Do not leak tty_driver structure on each module removal. Also do
proper frees in fail paths of module_init.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Jan Dumon <j.dumon@option.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>