ARM: dts: bcm2711: enable PHY link energy detect powerdown via DT

Add brcm,powerdown-enable to the external PHY nodes on Pi 4B and CM4.
This puts the BCM54210PE PHY into a low-power state when the link is
down, reducing power consumption when no cable is connected. This is
the same approach already used by Pi 5 and CM5.

Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>

Author: nbuchwitz

arch/arm/boot/dts/broadcom/bcm2711-rpi-4-b.dts

@@ -213,6 +213,7 @@
 	phy1: ethernet-phy@1 {
 		/* No PHY interrupt */
 		reg = <0x1>;
+		brcm,powerdown-enable;
 
 		leds {
 			#address-cells = <1>;

arch/arm/boot/dts/broadcom/bcm2711-rpi-cm4.dts

@@ -216,6 +216,7 @@
 	phy1: ethernet-phy@0 {
 		/* No PHY interrupt */
 		reg = <0x0>;
+		brcm,powerdown-enable;
 	};
 };