USB: serial: fix memleak in driver-registration error path

udriver struct allocated by kzalloc() will not be freed
if usb_register() and next calls fail. This patch fixes this
by adding one more step with kfree(udriver) in error path.
Signed-off-by: Alexey Klimov <klimov.linux@gmail.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/usb-serial.c

@@ -1433,7 +1433,7 @@ int usb_serial_register_drivers(struct usb_serial_driver *const serial_drivers[]
 
 	rc = usb_register(udriver);
 	if (rc)
-		return rc;
+		goto failed_usb_register;
 
 	for (sd = serial_drivers; *sd; ++sd) {
 		(*sd)->usb_driver = udriver;
@@ -1451,6 +1451,8 @@ int usb_serial_register_drivers(struct usb_serial_driver *const serial_drivers[]
 	while (sd-- > serial_drivers)
 		usb_serial_deregister(*sd);
 	usb_deregister(udriver);
+failed_usb_register:
+	kfree(udriver);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(usb_serial_register_drivers);