sctp: do not pr_err for the duplicated node in transport rhlist

The pr_err in sctp_hash_transport was supposed to report a sctp bug
for using rhashtable/rhlist.

The err '-EEXIST' introduced in Commit cd2b70875058 ("sctp: check
duplicate node before inserting a new transport") doesn't belong
to that case.

So just return -EEXIST back without pr_err any kmsg.

Fixes: cd2b70875058 ("sctp: check duplicate node before inserting a new transport")
Reported-by: Wei Chen <weichen@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/input.c

@@ -897,15 +897,12 @@ int sctp_hash_transport(struct sctp_transport *t)
 	rhl_for_each_entry_rcu(transport, tmp, list, node)
 		if (transport->asoc->ep == t->asoc->ep) {
 			rcu_read_unlock();
-			err = -EEXIST;
-			goto out;
+			return -EEXIST;
 		}
 	rcu_read_unlock();
 
 	err = rhltable_insert_key(&sctp_transport_hashtable, &arg,
 				  &t->node, sctp_hash_params);
-
-out:
 	if (err)
 		pr_err_once("insert transport fail, errno %d\n", err);