arm64: dts: imx8mp-phyboard-pollux-rdk: Fix led sub-node names

Dtschema of the leds sub-node names expects "led-1" instead of led1.
So, the sub-node names are corrected according to the regexes.
Signed-off-by: Yashwanth Varakala <y.varakala@phytec.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mp-phyboard-pollux-rdk.dts

@@ -76,15 +76,15 @@ leds@62 {
 		compatible = "nxp,pca9533";
 		reg = <0x62>;
 
-		led1 {
+		led-1 {
 			type = <PCA9532_TYPE_LED>;
 		};
 
-		led2 {
+		led-2 {
 			type = <PCA9532_TYPE_LED>;
 		};
 
-		led3 {
+		led-3 {
 			type = <PCA9532_TYPE_LED>;
 		};
 	};