Merge branch 'stacked-vlan-TSO'

Toshiaki Makita says:

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Stacked vlan TSO for virtual devices

Basically virtual devices do not need to segment double tagged packets.
This patch set adds TSO feature for double tagged packets to several
virtual devices, which can be realized by simply setting
.ndo_features_check to passthru_features_check.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>