TTY: hso, remove tty NULL checks fro tty->ops

tty is never NULL in tty->ops->* while the device is open. (And they
are not called otherwise.) So remove pointless checks and use
tty->driver_data directly.

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