net: ethtool: Add support for new power domains index description

Report the index of the newly introduced PSE power domain to the user,
enabling improved management of the power budget for PSE devices.

Signed-off-by: Kory Maincent (Dent Project) <kory.maincent@bootlin.com>
Reviewed-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://patch.msgid.link/20250617-feature_poe_port_prio-v14-5-78a1a645e2ee@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/ethtool.yaml

@@ -1406,6 +1406,10 @@ attribute-sets:
         type: nest
         multi-attr: true
         nested-attributes: c33-pse-pw-limit
+      -
+        name: pse-pw-d-id
+        type: u32
+        name-prefix: ethtool-a-
   -
     name: rss
     attr-cnt-name: __ethtool-a-rss-cnt
@@ -2229,6 +2233,7 @@ operations:
             - c33-pse-ext-substate
             - c33-pse-avail-pw-limit
             - c33-pse-pw-limit-ranges
+            - pse-pw-d-id
       dump: *pse-get-op
     -
       name: pse-set