tty_port,usb-console: Fix usb serial console open/close regression

Commit e1108a63e10d344284011cccc06328b2cd3e5da3 ("usb_serial: Use the
shutdown() operation") breaks the ability to use a usb console
starting in 2.6.33. This was observed when using
console=ttyUSB0,115200 as a boot argument with an FTDI device. The
error is:

ftdi_sio ttyUSB0: ftdi_submit_read_urb - failed submitting read urb, error -22

The handling of the ASYNCB_INITIALIZED changed in 2.6.32 such that in
tty_port_shutdown() it always clears the flag if it is set. The fix
is to add a variable to the tty_port struct to indicate when the tty
port is a console.

CC: Alan Cox <[e-mail]>
CC: Alan Stern <[e-mail]>
CC: Oliver Neukum <[e-mail]>
CC: Andrew Morton <[e-mail]>
Signed-off-by: Jason Wessel <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/char/tty_port.c

···
 static void tty_port_shutdown(struct tty_port *port)
 {
 	mutex_lock(&port->mutex);
-	if (port->ops->shutdown &&
+	if (port->ops->shutdown && !port->console &&
 		test_and_clear_bit(ASYNCB_INITIALIZED, &port->flags))
 			port->ops->shutdown(port);
 	mutex_unlock(&port->mutex);

drivers/usb/serial/console.c

···
 	/* The console is special in terms of closing the device so
 	 * indicate this port is now acting as a system console. */
 	port->console = 1;
+	port->port.console = 1;
 
 	mutex_unlock(&serial->disc_mutex);
 	return retval;

include/linux/tty.h

···
 	wait_queue_head_t	close_wait;	/* Close waiters */
 	wait_queue_head_t	delta_msr_wait;	/* Modem status change */
 	unsigned long		flags;		/* TTY flags ASY_*/
+	unsigned char		console:1;	/* port is a console */
 	struct mutex		mutex;		/* Locking */
 	struct mutex		buf_mutex;	/* Buffer alloc lock */
 	unsigned char		*xmit_buf;	/* Optional buffer */