USB: serial: drop obsolete open-race workaround

Commit a65a6f14dc24 ("USB: serial: fix race between probe and open")
fixed a race between probe and open, which could lead to crashes when a
not yet fully initialised port was being opened.

This race was later incidentally closed by commit 7e73eca6a7b2 ("TTY:
move cdev_add to tty_register_device") which moved character-device
registration from tty_register_driver to tty_register_device, which
isn't called until the port has been fully set up.

Remove the now redundant workaround which had the negative side effect
of not allowing a port to be opened immediately after user space had
been notified of a new tty device.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/usb-serial.c

@@ -996,12 +996,6 @@ static int usb_serial_probe(struct usb_interface *interface,
 		serial->attached = 1;
 	}
 
-	/* Avoid race with tty_open and serial_install by setting the
-	 * disconnected flag and not clearing it until all ports have been
-	 * registered.
-	 */
-	serial->disconnected = 1;
-
 	if (allocate_minors(serial, num_ports)) {
 		dev_err(ddev, "No more free serial minor numbers\n");
 		goto probe_error;
@@ -1019,8 +1013,6 @@ static int usb_serial_probe(struct usb_interface *interface,
 			dev_err(ddev, "Error registering port device, continuing\n");
 	}
 
-	serial->disconnected = 0;
-
 	if (num_ports > 0)
 		usb_serial_console_init(serial->port[0]->minor);
 exit: