network/parse-ip-opts.sh: bind enx* interface to the MAC

do it automatically for the persistent naming scheme

modules.d/40network/parse-ip-opts.sh

@@ -113,6 +113,16 @@ for p in $(getargs ip=); do
         die "Server-ip or dhcp for netboot needed, but current arguments say otherwise"
     fi
 
+    if str_starts "$dev" "enx" && [ ${#dev} -eq 15 ]; then
+        printf -- "ifname=%s:%s:%s:%s:%s:%s:%s\n" \
+               "$dev" \
+               "${dev:3:2}" \
+               "${dev:5:2}" \
+               "${dev:7:2}" \
+               "${dev:9:2}" \
+               "${dev:11:2}" \
+               "${dev:13:2}" >> /etc/cmdline.d/80-enx.conf
+    fi
 done
 
 # put BOOTIF in IFACES to make sure it comes up