powerpc/fsl_pmc: use builtin_platform_driver

Use builtin_platform_driver() helper to simplify the code.
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Scott Wood <oss@buserror.net>

arch/powerpc/sysdev/fsl_pmc.c

@@ -85,8 +85,4 @@ static struct platform_driver pmc_driver = {
 	.probe = pmc_probe,
 };
 
-static int __init pmc_init(void)
-{
-	return platform_driver_register(&pmc_driver);
-}
-device_initcall(pmc_init);
+builtin_platform_driver(pmc_driver);