netlink: Unneeded local variable

We already have a variable, which has the same capability.
Signed-off-by: Wang Chen <wangchen@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netlink/af_netlink.c

@@ -886,7 +886,7 @@ retry:
 		return netlink_unicast_kernel(sk, skb);
 
 	if (sk_filter(sk, skb)) {
-		int err = skb->len;
+		err = skb->len;
 		kfree_skb(skb);
 		sock_put(sk);
 		return err;