net/act_pedit: fix an error code

I'm reviewing static checker warnings where we do ERR_PTR(0), which is
the same as NULL.  I'm pretty sure we intended to return ERR_PTR(-EINVAL)
here.  Sometimes these bugs lead to a NULL dereference but I don't
immediately see that problem here.

Fixes: 71d0ed7079df ("net/act_pedit: Support using offset relative to the conventional network headers")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Amir Vadai <amir@vadai.me>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/act_pedit.c

@@ -94,8 +94,10 @@ static struct tcf_pedit_key_ex *tcf_pedit_keys_ex_parse(struct nlattr *nla,
 		k++;
 	}
 
-	if (n)
+	if (n) {
+		err = -EINVAL;
 		goto err_out;
+	}
 
 	return keys_ex;