mediatek: fix failsafe ethernet for NWA50AX Pro

The NWA50AX Pro only has a eth0 interface for its only ethernet port.
Use this port for preinit.

Fixes non-working network in failsafe mode.

Signed-off-by: David Bauer <[email protected]>

target/linux/mediatek/base-files/lib/preinit/05_set_preinit_iface

@@ -9,7 +9,8 @@ set_preinit_iface() {
 		ip link set eth1 up
 		ifname=eth1
 		;;
-	ubnt,unifi-6-lr)
+	ubnt,unifi-6-lr|\
+	zyxel,nwa50ax-pro)
 		ip link set eth0 up
 		ifname=eth0
 		;;