dts64: add second gmac for r64

use it with vlan-aware bridge

- create a bridge for use for wan

    /etc/systemd/network/11-wanbr.netdev
    [NetDev]
    Name=wanbr
    Kind=bridge

    [Bridge]
    DefaultPVID=0 # should be different to other vlan-aware bridges (like lanbr)
    VLANFiltering=1

- map aux and wan to vlan-aware bridge
- traffic will be tagged inside with vlan-id 99

    /etc/systemd/network/12-wanbr-bind.network
    [Match]
    Name=wan aux

    [Link]
    RequiredForOnline=no

    [Network]
    BindCarrier=eth0
    Bridge=wanbr

    [BridgeVLAN]
    VLAN=99
    PVID=99
    EgressUntagged=99

- put wanbr up by default

    /etc/systemd/network/13-wanbr.network
    [Match]
    Name=wanbr

    [Network]
    BindCarrier=eth0
    ConfigureWithoutCarrier=true

- configure eth1 as wan

    /etc/systemd/network/15-wan.network
    [Match]
    Name=eth1

    [Network]
    BindCarrier=eth0

    Address=192.168.0.18/24
    Gateway=192.168.0.10
    DNS=192.168.0.10

    IPForward=yes

arch/arm64/boot/dts/mediatek/mt7622-bananapi-bpi-r64.dts

@@ -185,6 +185,18 @@
 					label = "lan3";
 				};
 
+				port@5 {
+					reg = <5>;
+					label = "aux";
+					phy-mode = "rgmii";
+
+					fixed-link {
+						speed = <1000>;
+						full-duplex;
+						pause;
+					};
+				};
+
 				port@6 {
 					reg = <6>;
 					label = "cpu";