staging: speakup: use tty_kopen and tty_kclose

This patch replaces call to tty_open_by_driver with a tty_kopen and
uses tty_kclose instead of tty_release_struct to close it.

Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>