ixgbevf: Enables TSO for stacked VLAN

Setting ndo_features_check to passthru_features_check allows the driver
to skip the check for multiple tagged TSO packets and enables stacked
VLAN TSO.
Tested with 82599ES.

Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>