bnx2x: add gro_check

The patch provides workaround for BUG in FW 7.2.16,
which in GRO mode may miscalculate buffer and
place on SGE one frag less than it could.
It may happen only for some MTUs, we mark these MTUs
with gro_check flag during device initialization or
MTU change.

Next FW should include fix for the issue and the
patch could be reverted.

Signed-off-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>