ARM: dts: sun5i: Add backlight GPIO for reference design tablet

Now that we support the GPIOs on the AXP209, we can control the LCD
backlight with them.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

arch/arm/boot/dts/sun5i-reference-design-tablet.dtsi

@@ -54,7 +54,7 @@ backlight: backlight {
 		pwms = <&pwm 0 50000 PWM_POLARITY_INVERTED>;
 		brightness-levels = <0 10 20 30 40 50 60 70 80 90 100>;
 		default-brightness-level = <8>;
-		/* TODO: backlight uses axp gpio1 as enable pin */
+		enable-gpios = <&axp_gpio 1 GPIO_ACTIVE_HIGH>; /* AXP GPIO1 */
 	};
 
 	chosen {