Added initial VLAN support with vdev devices

Added initial VLAN support with vdev devices

For kernel supported devices, add for vlan tag support
This can be configured through port parameter:
vlan tag=<vlan tag>
If this parameter is set, a vlan tagged interface is created
on top of the tap device
This is only supported for vdev tap devices

When sending (untagged) packet to the tap device (through socket)
the tap should react in sending tagged packet

Note that receiving in L3 mode (w/o tap support) a tagged packet
is not yet supported.

Change-Id: I363fa2f8d2341ac41ef23620222ece1d944bf336
Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>