drivers/ieee802154/at86rf230: replace the code under _init and _exit by macro

The code under _init and _exit functions is similar to the code of
module_spi_driver macro, which is a wrapper to the module_driver macro,
so use it instead.
Signed-off-by: Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
Cc: Devendra Naga <develkernel412222@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/ieee802154/at86rf230.c

@@ -952,17 +952,7 @@ static struct spi_driver at86rf230_driver = {
 	.resume     = at86rf230_resume,
 };
 
-static int __init at86rf230_init(void)
-{
-	return spi_register_driver(&at86rf230_driver);
-}
-module_init(at86rf230_init);
-
-static void __exit at86rf230_exit(void)
-{
-	spi_unregister_driver(&at86rf230_driver);
-}
-module_exit(at86rf230_exit);
+module_spi_driver(at86rf230_driver);
 
 MODULE_DESCRIPTION("AT86RF230 Transceiver Driver");
 MODULE_LICENSE("GPL v2");