qeth: layer 3 support vlan IPv6 on hiper socket

hiper socket require the QETH_HDR_EXT_VLAN_FRAME flag in the
qdio header to handle vlan tagged frames.

Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>