USB: serial: sierra.c: use module_usb_serial_driver

This converts the sierra.c driver to use the module_usb_serial_driver() call
instead of having to have a module_init/module_exit function, saving a lot
of duplicated code.

CC: Alan Stern <stern@rowland.harvard.edu>
CC: Rusty Russell <rusty@rustcorp.com.au>
CC: Johan Hovold <jhovold@gmail.com>
CC: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/sierra.c

@@ -1115,25 +1115,7 @@ static struct usb_serial_driver * const serial_drivers[] = {
 	&sierra_device, NULL
 };
 
-/* Functions used by new usb-serial code. */
-static int __init sierra_init(void)
-{
-	int retval;
-
-	retval = usb_serial_register_drivers(&sierra_driver, serial_drivers);
-	if (retval == 0)
-		printk(KERN_INFO KBUILD_MODNAME ": " DRIVER_VERSION ":"
-			       DRIVER_DESC "\n");
-	return retval;
-}
-
-static void __exit sierra_exit(void)
-{
-	usb_serial_deregister_drivers(&sierra_driver, serial_drivers);
-}
-
-module_init(sierra_init);
-module_exit(sierra_exit);
+module_usb_serial_driver(sierra_driver, serial_drivers);
 
 MODULE_AUTHOR(DRIVER_AUTHOR);
 MODULE_DESCRIPTION(DRIVER_DESC);