[BNX2]: Fix TSO problem with small MSS.

Remove the check for skb->len greater than MTU when doing TSO.  When
the destination has a smaller MSS than the source, a TSO packet may
be smaller than the MTU at the source and we still need to process it
as a TSO packet.

Thanks to Brian Ristuccia <bristuccia@starentnetworks.com> for
reporting the problem.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>