net/mlx5e: E-Switch, Maintain vhca_id to vport_num mapping

Following patches in the series need to be able to map VF netdev to vport.
Since it is trivial to obtain vhca_id from netdev, maintain mapping from
vhca_id to vport_num inside eswitch offloads using xarray. Provide function
mlx5_eswitch_vhca_id_to_vport() to be used by TC code in following patches
to obtain the mapping.

Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: Dmytro Linkin <dlinkin@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>