ar71xx: register the gpio driver earlier

This allows gpio requests from mach files to succeed.

Signed-off-by: Felix Fietkau <nbd@nbd.name>

target/linux/ar71xx/patches-4.4/004-register_gpio_driver_earlier.patch

@@ -0,0 +1,15 @@
+HACK: register the GPIO driver earlier to ensure that gpio_request calls
+from mach files succeed.
+
+--- a/drivers/gpio/gpio-ath79.c
++++ b/drivers/gpio/gpio-ath79.c
+@@ -202,4 +202,8 @@ static struct platform_driver ath79_gpio
+ 	.probe = ath79_gpio_probe,
+ };
+ 
+-module_platform_driver(ath79_gpio_driver);
++static int __init ath79_gpio_init(void)
++{
++	return platform_driver_register(&ath79_gpio_driver);
++}
++postcore_initcall(ath79_gpio_init);