pinctrl: stm32: use builtin_platform_driver

Use builtin_platform_driver() helper to simplify the code.
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/stm32/pinctrl-stm32f429.c

@@ -1584,8 +1584,4 @@ static struct platform_driver stm32f429_pinctrl_driver = {
 	},
 };
 
-static int __init stm32f429_pinctrl_init(void)
-{
-	return platform_driver_register(&stm32f429_pinctrl_driver);
-}
-device_initcall(stm32f429_pinctrl_init);
+builtin_platform_driver(stm32f429_pinctrl_driver);