l2tp: cleanup l2tp_tunnel_delete calls

l2tp_tunnel_delete does not return anything since commit 62b982eeb458
("l2tp: fix race condition in l2tp_tunnel_delete").  But call sites of
l2tp_tunnel_delete still do casts to void to avoid unused return value
warnings.

Kill these now useless casts.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Sabrina Dubroca <sd@queasysnail.net>
Cc: Guillaume Nault <g.nault@alphalink.fr>
Cc: David S. Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Acked-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/l2tp/l2tp_core.c

@@ -1891,7 +1891,7 @@ static __net_exit void l2tp_exit_net(struct net *net)
 
 	rcu_read_lock_bh();
 	list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
-		(void)l2tp_tunnel_delete(tunnel);
+		l2tp_tunnel_delete(tunnel);
 	}
 	rcu_read_unlock_bh();
 

net/l2tp/l2tp_netlink.c

@@ -282,7 +282,7 @@ static int l2tp_nl_cmd_tunnel_delete(struct sk_buff *skb, struct genl_info *info
 	l2tp_tunnel_notify(&l2tp_nl_family, info,
 			   tunnel, L2TP_CMD_TUNNEL_DELETE);
 
-	(void) l2tp_tunnel_delete(tunnel);
+	l2tp_tunnel_delete(tunnel);
 
 	l2tp_tunnel_dec_refcount(tunnel);