ARM: dts: imx6qdl-phytec: Add LED labels

This allows boards the option of adding properties or disabling the
LEDs entirely.

Signed-off-by: Alexander Shiyan <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

arch/arm/boot/dts/imx6qdl-phytec-pfla02.dtsi

···
 		pinctrl-0 = <&pinctrl_leds>;
 		compatible = "gpio-leds";
 
-		green {
+		led_green: green {
 			label = "phyflex:green";
 			gpios = <&gpio1 30 0>;
 		};
 
-		red {
+		led_red: red {
 			label = "phyflex:red";
 			gpios = <&gpio2 31 0>;
 		};