Several functions need to access mlx5_vport and vport_num.
When these functions are called, caller already has mlx5_vport*
available.
Hence pass such mlx5_vport pointer.
This is preparation patch to add error checks to
mlx5_eswitch_get_vport() and to return error status.
By doing so, reduce places where error check of mlx5_eswitch_get_vport()
can be avoided.
While doing such change, mlx5_eswitch_query_vport_drop_stats() gets
corrected to work on vport, instead of vport_idx.