arch: arm64: dts: ti: add M4 LED wrapper for PFC 750-8400

The PFC 750-8400 board uses an M4 coprocessor to drive system
LEDs. Add the wago,m4-led-wrapper node to expose sys, run, io,
em and four user LEDs via the remoteproc firmware interface.
The sys LED defaults to an orange timer trigger on boot.

Signed-off-by: Heinrich Toews <ht@twx-software.de>

arch/arm64/boot/dts/ti/k3-am623-pfc-750-8400.dts

@@ -22,6 +22,56 @@
 		ethernet0 = &cpsw_port2;
 		ethernet1 = &cpsw_port1;
 	};
+
+	leds-m4 {
+		compatible = "wago,m4-led-wrapper";
+		remoteproc = <&mcu_m4fss>;
+		firmware-name = "wago-led-server-app.elf";
+		wago,reset-on-init;
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		led@0 {
+			reg = <0>;
+			label = "sys";
+			linux,default-trigger = "timer";
+			led-default-intensity = <255 80 0 64>; /* Orange, brightness 64/255 */
+		};
+
+		led@1 {
+			reg = <1>;
+			label = "run";
+		};
+
+		led@2 {
+			reg = <2>;
+			label = "io";
+		};
+
+		led@3 {
+			reg = <3>;
+			label = "em";
+		};
+
+		led@4 {
+			reg = <4>;
+			label = "u1";
+		};
+
+		led@5 {
+			reg = <5>;
+			label = "u2";
+		};
+
+		led@6 {
+			reg = <6>;
+			label = "u3";
+		};
+
+		led@7 {
+			reg = <7>;
+			label = "u4";
+		};
 };
 
 &wsysinit {