qeth: l3 ipv6 vlan not working on shared OSA chpid

In layer 3 mode IPv6 over VLAN does not work on newer OSA  levels in
case the sender and receiver run on the same (shared) OSA adapter.
Keep vlan info in the skb so the qdio header is filled with the
required vlan tag.

Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>