ARM: dts: stm32: update led nodes names for stm32f769-disco

Update led nodes names to be aligned with yaml description

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32f769-disco.dts

@@ -66,11 +66,11 @@
 
 	leds {
 		compatible = "gpio-leds";
-		green {
+		led-green {
 			gpios = <&gpioj 5 GPIO_ACTIVE_HIGH>;
 			linux,default-trigger = "heartbeat";
 		};
-		red {
+		led-red {
 			gpios = <&gpioj 13 GPIO_ACTIVE_HIGH>;
 		};
 	};