staging: mt7621-pinctrl: replace core_initcall_sync with builtin_platform_driver

We don't really need initialization of this at such an early stage.
Just use builtin_platform_driver to initialize this driver.
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/mt7621-pinctrl/pinctrl-rt2880.c

@@ -422,9 +422,4 @@ static struct platform_driver rt2880_pinmux_driver = {
 	},
 };
 
-int __init rt2880_pinmux_init(void)
-{
-	return platform_driver_register(&rt2880_pinmux_driver);
-}
-
-core_initcall_sync(rt2880_pinmux_init);
+builtin_platform_driver(rt2880_pinmux_driver);