net: fib_rules: fix error code for unsupported families

The errno code returned must be negative.

Fixes "RTNETLINK answers: Unknown error 18446744073709551519".
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/fib_rules.c

@@ -226,7 +226,7 @@ static int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 
 	ops = lookup_rules_ops(net, frh->family);
 	if (ops == NULL) {
-		err = EAFNOSUPPORT;
+		err = -EAFNOSUPPORT;
 		goto errout;
 	}
 
@@ -365,7 +365,7 @@ static int fib_nl_delrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 
 	ops = lookup_rules_ops(net, frh->family);
 	if (ops == NULL) {
-		err = EAFNOSUPPORT;
+		err = -EAFNOSUPPORT;
 		goto errout;
 	}