netlink: specs: rt-link: add notification for newlink

Add a notification entry for netlink so that we can test ntf handling
in classic netlink and C.

Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250418021706.1967583-9-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/rt-link.yaml

@@ -2420,6 +2420,12 @@ operations:
             - gso-ipv4-max-size
             - gro-ipv4-max-size
             - af-spec
+    -
+      name: newlink-ntf
+      doc: Notify that a link has been created
+      value: 16
+      notify: getlink
+      fixed-header: ifinfomsg
     -
       name: dellink
       doc: Delete an existing link.