ARM: dts: at91: nattis: initialize the BLON pin as output-low early

The pwm-backlight driver initializes BLON (the enable gpio) to
output-high if the gpio is input on probe. Initializing the gpio
to output-low before the driver probes prevents this action by
the pwm-backlight driver and gets rid of a nasty blink of full
backlight with an uninitialized panel.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

arch/arm/boot/dts/at91-nattis-2-natte-2.dts

@@ -60,6 +60,8 @@ panel_bl: backlight {
 
 		power-supply = <&bl_reg>;
 		enable-gpios = <&pioA 20 GPIO_ACTIVE_HIGH>;
+		pinctrl-names = "default";
+		pinctrl-0 = <&pinctrl_blon>;
 	};
 
 	panel: panel {
@@ -164,6 +166,12 @@ pinctrl_lvds_hipow0: lvds_hipow0 {
 				      (AT91_PINCTRL_OUTPUT |
 				       AT91_PINCTRL_OUTPUT_VAL(0))>;
 		};
+
+		pinctrl_blon: blon {
+			atmel,pins = <AT91_PIOA 20 AT91_PERIPH_GPIO
+				      (AT91_PINCTRL_OUTPUT |
+				       AT91_PINCTRL_OUTPUT_VAL(0))>;
+		};
 	};
 };