gpio-backlight: Discover driver during boot time

The gpio-backlight driver seems to be missing the
MODULE_DEVICE_TABLE line which is preventing it from
being modprobed during boot time even if the
gpio-backlight device exists.

This seems to be a bug and this patch attempts to
fix that.
Signed-off-by: NArun Bharadwaj <arun@gumstix.com>
Signed-off-by: NAsh Charles <ashcharles@gmail.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/video/backlight/gpio_backlight.c

@@ -146,6 +146,8 @@ static struct of_device_id gpio_backlight_of_match[] = {
 	{ .compatible = "gpio-backlight" },
 	{ /* sentinel */ }
 };
+
+MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
 #endif
 
 static struct platform_driver gpio_backlight_driver = {