bnxt_en: Support IFF_SUPP_NOFCS feature to transmit without ethernet FCS.

If firmware is capable, set the IFF_SUPP_NOFCS flag to support the
sockets option to transmit packets without FCS.  This is mainly used
for testing.

Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>