tun: Remove a dead line of code

Remove an unnecessary assignment.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index c3927b4..92ffd11 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -995,7 +995,6 @@
 				goto err_free_sk;
 		}
 
-		err = -EINVAL;
 		err = register_netdevice(tun->dev);
 		if (err < 0)
 			goto err_free_sk;