net/mlx5: E-Switch, Use vport index when init rep

Driver is referring to the array index when doing rep initialization,
using vport is confusing as it's normally interpreted as vport number.

This patch doesn't change any functionality.

Signed-off-by: Bodong Wang <bodong@mellanox.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>