clk: gxbb: use builtin_platform_driver to simplify the code

Use the builtin_platform_driver() macro to make the code simpler.
Signed-off-by: Wei Yongjun <weiyj.lk@gmail.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

drivers/clk/meson/gxbb.c

@@ -937,8 +937,4 @@ static struct platform_driver gxbb_driver = {
 	},
 };
 
-static int __init gxbb_clkc_init(void)
-{
-	return platform_driver_register(&gxbb_driver);
-}
-device_initcall(gxbb_clkc_init);
+builtin_platform_driver(gxbb_driver);