memory: atmel-sdramc: use builtin_platform_driver to simplify the code

Use the builtin_platform_driver() macro to make the code simpler.
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/memory/atmel-sdramc.c

@@ -85,8 +85,4 @@ static struct platform_driver atmel_ramc_driver = {
 	},
 };
 
-static int __init atmel_ramc_init(void)
-{
-	return platform_driver_register(&atmel_ramc_driver);
-}
-device_initcall(atmel_ramc_init);
+builtin_platform_driver(atmel_ramc_driver);