netlink: specs: mptcp: add missing 'server-side' attr

This attribute is added with the 'created' and 'established' events, but
the documentation didn't mention it.

Fixes: 41b3c69 ("mptcp: expose server_side attribute in MPTCP netlink events")
Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>

Author: matttbe

Documentation/netlink/specs/mptcp_pm.yaml

@@ -23,15 +23,17 @@ definitions:
      -
       name: created
       doc:
-        token, family, saddr4 | saddr6, daddr4 | daddr6, sport, dport
+        token, family, saddr4 | saddr6, daddr4 | daddr6, sport, dport,
+        server-side
         A new MPTCP connection has been created. It is the good time to
         allocate memory and send ADD_ADDR if needed. Depending on the
         traffic-patterns it can take a long time until the
         MPTCP_EVENT_ESTABLISHED is sent.
      -
       name: established
       doc:
-        token, family, saddr4 | saddr6, daddr4 | daddr6, sport, dport
+        token, family, saddr4 | saddr6, daddr4 | daddr6, sport, dport,
+        server-side
         A MPTCP connection is established (can start new subflows).
      -
       name: closed