RDMA/mlx5: Consolidate into special function all create QP calls

Finish separation to blocks of mlx5_ib_create_qp() functions,
so all internal create QP implementation are located in one place.

Link: https://lore.kernel.org/r/20200427154636.381474-36-leon@kernel.org


Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>