ARM: dts: bcm283x-rpi-lan7515: Enable Ethernet LEDs

Since the LAN7515 on Raspberry Pi 3B+ doesn't have an EEPROM and the OTP
is empty, we need to enable the Ethernet LEDs via Device Tree.
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>

arch/arm/boot/dts/bcm283x-rpi-lan7515.dtsi

 // SPDX-License-Identifier: GPL-2.0
+#include <dt-bindings/net/microchip-lan78xx.h>
+
 / {
 	aliases {
 		ethernet0 = &ethernet;
@@ -21,6 +23,18 @@ usb-port@1 {
 			ethernet: ethernet@1 {
 				compatible = "usb424,7800";
 				reg = <1>;
+
+				mdio {
+					#address-cells = <0x1>;
+					#size-cells = <0x0>;
+					eth_phy: ethernet-phy@1 {
+						reg = <1>;
+						microchip,led-modes = <
+							LAN78XX_LINK_1000_ACTIVITY
+							LAN78XX_LINK_10_100_ACTIVITY
+						>;
+					};
+				};
 			};
 		};
 	};