net/mlx5: E-switch, Generalize per vport table API

Currently, per vport table was used only for port mirroring actions.
However, sample action will also require a per vport table instance.

Generalize the vport table API to work with multiple namespaces where
each namespace manages its own vport table instance.

Signed-off-by: Chris Mi <cmi@nvidia.com>
Reviewed-by: Oz Shlomo <ozsh@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>