net: bonding: correctly annotate RCU in bond_should_notify_peers()

RCU use in bond_should_notify_peers() looks wrong, since it does
rcu_dereference(), leaves the critical section, and uses the
pointer after that.

Luckily, it's called either inside a nested RCU critical section
or with the RTNL held.

Annotate it with rcu_dereference_rtnl() instead, and remove the
inner RCU critical section.

Fixes: 4cb4f97 ("bonding: rebuild the lock use for bond_mii_monitor()")
Reviewed-by: Jiri Pirko <[email protected]>
Signed-off-by: Johannes Berg <[email protected]>
Acked-by: Jay Vosburgh <[email protected]>
Link: https://patch.msgid.link/20240719094119.35c62455087d.I68eb9c0f02545b364b79a59f2110f2cf5682a8e2@changeid
Signed-off-by: Paolo Abeni <[email protected]>

drivers/net/bonding/bond_main.c

@@ -1121,13 +1121,10 @@ static struct slave *bond_find_best_slave(struct bonding *bond)
 	return bestslave;
 }
 
+/* must be called in RCU critical section or with RTNL held */
 static bool bond_should_notify_peers(struct bonding *bond)
 {
-	struct slave *slave;
-
-	rcu_read_lock();
-	slave = rcu_dereference(bond->curr_active_slave);
-	rcu_read_unlock();
+	struct slave *slave = rcu_dereference_rtnl(bond->curr_active_slave);
 
 	if (!slave || !bond->send_peer_notif ||
 	    bond->send_peer_notif %