bnx2x: fix tunneled GSO over IPv6

Set correct bit for packed description.

Introduced in e42780b6
    bnx2x: Utilize FW 7.10.51

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Dmitry Kravkov <Dmitry.Kravkov@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>