feat(readme): update docs

Author: snowch

README.md

@@ -69,7 +69,7 @@ hpecp TAB
 Add gateway:
 ```sh
 hpecp lock create "Install Gateway"
-hpecp gateway create-with-ssh-key 10.1.0.5 my.gateway.local --ssh-key-file controller_private.key
+hpecp gateway create-with-ssh-key --ip 10.1.0.5 --proxy-node-hostname my.gateway.local --ssh-key-file controller_private.key
 hpecp lock delete-all
 ```