Instead of hand crafted mlx5_qp_context and mlx5_qp_path use common
MLX5_SET() macros.

Link: https://lore.kernel.org/r/20200526115440.205922-7-leon@kernel.orgReviewed-by: NMaor Gottlieb <maorg@mellanox.com>
Reviewed-by: NMark Zhang <markz@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>