[linux] Fix error control flow in tap_probe()

Signed-off-by: Michael Brown <mcb30@ipxe.org>
diff --git a/src/drivers/linux/tap.c b/src/drivers/linux/tap.c
index ff1e08b..9b52c20 100644
--- a/src/drivers/linux/tap.c
+++ b/src/drivers/linux/tap.c
@@ -231,9 +231,9 @@
 
 	return 0;
 
-err_settings:
 	unregister_netdev(netdev);
 err_register:
+err_settings:
 	netdev_nullify(netdev);
 	netdev_put(netdev);
 	return rc;