arm64: dts: mediatek: mt8173-elm: Add backlight enable pin config

Add the proper pinctrl for GPIO95 backlight enable pin and assign it
to the pwm-backlight node.
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20211102144224.457446-2-angelogioacchino.delregno@collabora.comSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>

arch/arm64/boot/dts/mediatek/mt8173-elm.dtsi

@@ -27,6 +27,8 @@ backlight: backlight {
 		power-supply = <&bl_fixed_reg>;
 		enable-gpios = <&pio 95 GPIO_ACTIVE_HIGH>;
 
+		pinctrl-names = "default";
+		pinctrl-0 = <&panel_backlight_en_pins>;
 		status = "okay";
 	};
 
@@ -825,6 +827,12 @@ pins_clk {
 		};
 	};
 
+	panel_backlight_en_pins: panel_backlight_en_pins {
+		pins1 {
+			pinmux = <MT8173_PIN_95_PCM_TX__FUNC_GPIO95>;
+		};
+	};
+
 	panel_fixed_pins: panel_fixed_pins {
 		pins1 {
 			pinmux = <MT8173_PIN_41_CMMCLK__FUNC_GPIO41>;