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: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index e3e9ab0..277a230 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -226,7 +226,7 @@
 
 	ops = lookup_rules_ops(net, frh->family);
 	if (ops == NULL) {
-		err = EAFNOSUPPORT;
+		err = -EAFNOSUPPORT;
 		goto errout;
 	}
 
@@ -365,7 +365,7 @@
 
 	ops = lookup_rules_ops(net, frh->family);
 	if (ops == NULL) {
-		err = EAFNOSUPPORT;
+		err = -EAFNOSUPPORT;
 		goto errout;
 	}