mpls-conf: T915: Add ethernet vif MPLS enable
mpls-conf: T915: Add ethernet vif MPLS enable

In this commit we added ethernet sub interface MPLS enablement. Per request by
@bbs2web, this functionality is now possible. This should now allow ethernet
switched networks with VLAN tags to also allow for MPLS packet flow.

vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x