net/mlx5: Refactor and expand rep vport stat group

Expand representor vport stat group to support all counters from the
vport stat group, to count all the traffic passing through the vport.

Fix current implementation where fill_stats and update_stats use
different structs.

Signed-off-by: Or Har-Toov <ohartoov@nvidia.com>
Reviewed-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>