netlink: specs: Introduce new netlink command to get current timestamp

Add a new commands allowing to get the current time stamping on a
netdevice's link.

Example usage :
./ynl/cli.py --spec netlink/specs/ethtool.yaml --no-schema --do ts-get \
	     --json '{"header":{"dev-name":"eth0"}}'
{'header': {'dev-index': 3, 'dev-name': 'eth0'}, 'ts-layer': 1}

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: kmaincent

Documentation/netlink/specs/ethtool.yaml

@@ -939,6 +939,16 @@ attribute-sets:
       -
         name: burst-tmr
         type: u32
+  -
+    name: ts
+    attributes:
+      -
+        name: header
+        type: nest
+        nested-attributes: header
+      -
+        name: ts-layer
+        type: u32
 
 operations:
   enum-model: directional
@@ -1689,3 +1699,17 @@ operations:
       name: mm-ntf
       doc: Notification for change in MAC Merge configuration.
       notify: mm-get
+    -
+      name: ts-get
+      doc: Get current timestamp
+
+      attribute-set: ts
+
+      do:
+        request:
+          attributes:
+            - header
+        reply:
+          attributes: &ts
+            - header
+            - ts-layer