common/mlx5: glue device and PD import

common/mlx5: glue device and PD import

Add support for rdma-core API to import device.
The API gets ibv_context file descriptor and returns an ibv_context
pointer that is associated with the given file descriptor.
Add also support for rdma-core API to import PD.
The API gets ibv_context and PD handle and returns a protection domain
(PD) that is associated with the given handle in the given context.

Signed-off-by: Michael Baum <michaelba@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>