net: vlan: drop current vlan interface naming

There were two problems about vlan interface naming currently.

1. When there were more than 1 vlan interfaces. It's not able to
   initialze name for all of them to same name VLAN-<free>.
2. When enabled vlan with tag, the name VLAN-xxx was used.
   However we may need to support multiple physical interfaces
   in the future. So, it's not able to use same name VLAN-xxx
   either for same tag on different physical interfaces.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>