networkd: add support for link files

networkd/defaults/main.yml

 ---
 
+# interfaces:
+#   - identifier: name_for_the_link_file
+#     match:
+#       PermanentMACAddress: "01:23:45:67:89:ab"
+#     link:
+#       Name: veryimportantinterface
+#
+
 # networkd:
 #   - type: 'dhcp'
 #   - type: 'static'