mlx4_en: Removed redundant check on lso header size

This check that verifies that the LSO header along with control
segment and first data segment do not cross 128 bytes is no longer
required.

Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>