tty: Add missing break statement

Being miss in first place.

For tty-major we either should understand the driver
we're handling, in the code above it's VT driver, so if minor
is pointing somewhere else -- it's unknown tty.

We need to look into every serial device we're going to
support if we can c/r it without problem. Thus 'break' prevent
us from potential problems.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/tty.c

@@ -275,6 +275,7 @@ struct tty_driver *get_tty_driver(dev_t rdev, dev_t dev)
 			 */
 			return &vt_driver;
 		/* Other minors points to UART serial ports */
+		break;
 	case USB_SERIAL_MAJOR:
 	case LOW_DENSE_SERIAL_MAJOR:
 		return &serial_driver;