RDMA/mlx5: Drop in-driver verbs object creations

There is no real value in bypassing IB/core APIs for creating standard
objects with standard types. The open-coded variant didn't have any
restrack task management calls and caused to such objects to be not
present when running rdmatoool.

Link: https://lore.kernel.org/r/f745590e5fb7d56f90fdb25f64ee3983ba17e1e4.1627040189.git.leonro@nvidia.com


Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>