net/mlx5: store protection domain number on create

net/mlx5: store protection domain number on create

Function mlx5_alloc_shared_ibctx() allocates Protection Domain using
verbs API, as part of shared IB device context.
This patch adds reading and storing of pdn value from the created PD
object, using DV API.
The pdn value is required when creating WQ using DevX API.

This patch also updates function flow_dv_create_counter_stat_mem_mng()
which uses the pdn value as well.

Signed-off-by: Dekel Peled <dekelp@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>