net/mlx5e: Use vhca_id in generating representor port_index

It is desired to use unique port indices when multiple pci devices'
devlink instance have the same switch-id.

Make use of vhca-id to generate such unique devlink port indices.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>