net/mlx5: add test for remote PD and CTX

net/mlx5: add test for remote PD and CTX

Add mlx5 internal option in testpmd similar to run-time function
"port attach" which adds another parameter named "socket" for attaching
port and add 2 devargs before.

The arguments are "cmd_fd" and "pd_handle" using to import device
created out of PMD. Testpmd application import it using IPC, and updates
the devargs list before attaching.

These arguments were added in
the commit 9d936f4f1a5e ("common/mlx5: support remote PD and CTX")

The syntax is:

  testpmd> mlx5 port attach (identifier) socket=(path)

Where "path" is the IPC socket path agreed on the remote process.

Signed-off-by: Michael Baum <michaelba@nvidia.com>
Reviewed-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Matan Azrad <matan@nvidia.com>