net: vrf: Fix setting NLM_F_EXCL flag when adding l3mdev rule

Only need 1 l3mdev FIB rule. Fix setting NLM_F_EXCL in the nlmsghdr.

Fixes: 1aa6c4f6b8cd8 ("net: vrf: Add l3mdev rules on first device create")
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
index d6988db..7d909c8 100644
--- a/drivers/net/vrf.c
+++ b/drivers/net/vrf.c
@@ -1128,7 +1128,7 @@
 		goto nla_put_failure;
 
 	/* rule only needs to appear once */
-	nlh->nlmsg_flags &= NLM_F_EXCL;
+	nlh->nlmsg_flags |= NLM_F_EXCL;
 
 	frh = nlmsg_data(nlh);
 	memset(frh, 0, sizeof(*frh));