myri10ge: Add vlan rx for better GRO perf.

Unlike LRO, GRO requires that vlan tags be removed before
aggregation can occur.  Since the myri10ge NIC does not support
hardware vlan tag offload, we must remove the tag in the driver
to achieve performance comparable to LRO for vlan tagged frames.

Thanks to Eric Duzamet for his help simplifying the original patch.

Signed-off-by: Andrew Gallatin <gallatin@myri.com>
Signed-off-by: David S. Miller <davem@davemloft.net>