FOU: Fix no return statement warning for !CONFIG_NET_FOU_IP_TUNNELS

net/ipv4/fou.c: In function ‘ip_tunnel_encap_del_fou_ops’:
net/ipv4/fou.c:861:1: warning: no return statement in function returning non-void [-Wreturn-type]

Fixes: a8c5f90fb5 ("ip_tunnel: Ops registration for secondary encap (fou, gue)")
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index fe09077..b0b436b 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -856,7 +856,7 @@
 	return 0;
 }
 
-static int ip_tunnel_encap_del_fou_ops(void)
+static void ip_tunnel_encap_del_fou_ops(void)
 {
 }