bnx2x: set gso_type

In LRO mode, bnx2x set gso_size but not gso type.
This leads to crashes in macvtap.
Commit cbf1de72
queued for 3.9 includes a more complete fix.
This is a minimal patch to avoid the crash, for 3.8.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>