tty: Export redirect release

This will be required by the pty code when it removes tty_vhangup() on
master close.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Link: https://lore.kernel.org/r/20201124004902.1398477-2-minyard@acm.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>