IB/mlx4: Fix struct mlx4_ib_create_wq alignment

The mlx4 ABI defines to have structures with alignment of 64B.

Fixes: 400b1ebc ("IB/mlx4: Add support for WQ related verbs")
Signed-off-by: Guy Levi <guyle@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>