RDMA/mlx5: Use MLX5_SET macro instead of local structure

Use generic mlx5 structure defined in mlx5_ifc.h to represent ConnectX
device data structures instead of using structure defined specifically for
mlx5_ib module.

Link: https://lore.kernel.org/r/20200716105248.1423452-3-leon@kernel.org
Signed-off-by: Meir Lichtinger <meirl@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>