netlink: specs: Add missing phy-ntf command to ethtool spec

ETHTOOL_MSG_PHY_NTF description is missing in the ethtool netlink spec.
Add it to the spec.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20241022151418.875424-1-kory.maincent@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kmaincent

Documentation/netlink/specs/ethtool.yaml

@@ -1956,3 +1956,7 @@ operations:
             - upstream-sfp-name
             - downstream-sfp-name
       dump: *phy-get-op
+    -
+      name: phy-ntf
+      doc: Notification for change in PHY devices.
+      notify: phy-get