net/mlx5: Fix the macro for accessing EC VF vports

The last value is not set correctly. This results in representors not
being created for all EC VFs when the base value is higher than 0.

Fixes: a7719b29 ("net/mlx5: Add management of EC VF vports")
Signed-off-by: Daniel Jurgens <danielj@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>