net/mlx5: probe all port representors

net/mlx5: probe all port representors

Probe existing port representors in addition to their master device and
associate them automatically.

To avoid collision between Ethernet devices, they are named as follows:

- "{DBDF}" for master/switch devices.
- "{DBDF}_representor_{rep}" with "rep" starting from 0 for port
  representors.

(Patch based on prior work from Yuanhan Liu)

Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Reviewed-by: Xueming Li <xuemingl@mellanox.com>