vti6: return GRE_KEY for vti6

Align vti6 with vti by returning GRE_KEY flag. This enables iproute2
to display tunnel keys on "ip -6 tunnel show"
Signed-off-by: David Forster <dforster@brocade.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_vti.c

@@ -693,6 +693,10 @@ vti6_parm_to_user(struct ip6_tnl_parm2 *u, const struct __ip6_tnl_parm *p)
 	u->link = p->link;
 	u->i_key = p->i_key;
 	u->o_key = p->o_key;
+	if (u->i_key)
+		u->i_flags |= GRE_KEY;
+	if (u->o_key)
+		u->o_flags |= GRE_KEY;
 	u->proto = p->proto;
 
 	memcpy(u->name, p->name, sizeof(u->name));