rtnetlink: fix error return code in rtnl_link_fill()

Fix to return a negative error code from the error handling case
instead of 0(possible overwrite to 0 by ops->fill_xstats call),
as returned elsewhere in this function.
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -496,8 +496,10 @@ static int rtnl_link_fill(struct sk_buff *skb, const struct net_device *dev)
 	}
 	if (ops->fill_info) {
 		data = nla_nest_start(skb, IFLA_INFO_DATA);
-		if (data == NULL)
+		if (data == NULL) {
+			err = -EMSGSIZE;
 			goto err_cancel_link;
+		}
 		err = ops->fill_info(skb, dev);
 		if (err < 0)
 			goto err_cancel_data;