Fix mtu option in documentation

Signed-off-by: Alessandro Boch <aboch@docker.com>

docs/reference/commandline/network_create.md

@@ -156,7 +156,7 @@ equivalent docker daemon flags used for docker0 bridge:
 | `com.docker.network.bridge.enable_ip_masquerade` | `--ip-masq` | Enable IP masquerading                                |
 | `com.docker.network.bridge.enable_icc`           | `--icc`     | Enable or Disable Inter Container Connectivity        |
 | `com.docker.network.bridge.host_binding_ipv4`    | `--ip`      | Default IP when binding container ports               |
-| `com.docker.network.mtu`                         | `--mtu`     | Set the containers network MTU                        |
+| `com.docker.network.driver.mtu`                  | `--mtu`     | Set the containers network MTU                        |
 
 The following arguments can be passed to `docker network create` for any
 network driver, again with their approximate equivalents to `docker daemon`.

docs/userguide/networking/work-with-networks.md

@@ -123,7 +123,7 @@ equivalent docker daemon flags used for docker0 bridge:
 | `com.docker.network.bridge.enable_ip_masquerade` | `--ip-masq` | Enable IP masquerading                                |
 | `com.docker.network.bridge.enable_icc`           | `--icc`     | Enable or Disable Inter Container Connectivity        |
 | `com.docker.network.bridge.host_binding_ipv4`    | `--ip`      | Default IP when binding container ports               |
-| `com.docker.network.mtu`                         | `--mtu`     | Set the containers network MTU                        |
+| `com.docker.network.driver.mtu`                  | `--mtu`     | Set the containers network MTU                        |
 
 The following arguments can be passed to `docker network create` for any network driver.