tty: remove unused tty_driver->termios_locked

This field is unused since 2.6.28 (commit fe6e29fdb1a7: "tty: simplify
ktermios allocation", to be exact)

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/tty_driver.h

@@ -312,7 +312,6 @@ struct tty_driver {
 	 */
 	struct tty_struct **ttys;
 	struct ktermios **termios;
-	struct ktermios **termios_locked;
 	void *driver_state;
 
 	/*