net/mlx4_core: Set CQE/EQE size to 64B by default

To achieve out of the box performance default is to use 64 byte CQE/EQE.
In tests that we conduct in our labs, we achieved a performance
improvement of twice the message rate. For older VF/libmlx4 support,
enable_64b_cqe_eqe must be set to 0 (disabled).

Signed-off-by: Eyal Perry <eyalpe@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>