gpio: ath79: Fix module autoload

If the driver is built as a module, autoload won't work because the module
alias information is not filled. So user-space can't match the registered
device with the corresponding module.

Export the module alias information using the MODULE_DEVICE_TABLE() macro.

Before this patch:

$ modinfo drivers/gpio/gpio-ath79.ko | grep alias
$

After this patch:

$ modinfo drivers/gpio/gpio-ath79.ko | grep alias
alias:          of:N*T*Cqca,ar9340-gpioC*
alias:          of:N*T*Cqca,ar9340-gpio
alias:          of:N*T*Cqca,ar7100-gpioC*
alias:          of:N*T*Cqca,ar7100-gpio

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Aban Bedel <albeu@free.fr>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-ath79.c

@@ -219,6 +219,7 @@ static const struct of_device_id ath79_gpio_of_match[] = {
 	{ .compatible = "qca,ar9340-gpio" },
 	{},
 };
+MODULE_DEVICE_TABLE(of, ath79_gpio_of_match);
 
 static int ath79_gpio_probe(struct platform_device *pdev)
 {