USB: serial: fix tty-device error handling at probe

Add missing error handling when registering the tty device at port
probe. This avoids trying to remove an uninitialised character device
when the port device is removed.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Takashi Iwai <tiwai@suse.de>
Cc: stable <stable@vger.kernel.org>	# v2.6.12
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/usb/serial/bus.c

@@ -51,6 +51,7 @@ static int usb_serial_device_probe(struct device *dev)
 {
 	struct usb_serial_driver *driver;
 	struct usb_serial_port *port;
+	struct device *tty_dev;
 	int retval = 0;
 	int minor;
 
@@ -80,7 +81,15 @@ static int usb_serial_device_probe(struct device *dev)
 	}
 
 	minor = port->minor;
-	tty_register_device(usb_serial_tty_driver, minor, dev);
+	tty_dev = tty_register_device(usb_serial_tty_driver, minor, dev);
+	if (IS_ERR(tty_dev)) {
+		retval = PTR_ERR(tty_dev);
+		device_remove_file(dev, &dev_attr_port_number);
+		if (driver->port_remove)
+			driver->port_remove(port);
+		goto exit_with_autopm;
+	}
+
 	dev_info(&port->serial->dev->dev,
 		 "%s converter now attached to ttyUSB%d\n",
 		 driver->description, minor);