The macro MLX4_IB_SQ_HEADROOM calculates the spare room needed to be
left. Use it instead of hard-coding the HW prefetch size.
Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>