net/mlx5e: Get the number of offloaded TC rules from the correct table

As we keep the offloaded TC rules for NIC and e-switch in two different
places, make sure to return the number of offloaded flows according
to the use-case and not blindly from the priv.

Fixes: 655dc3d2

 ('net/mlx5e: Use shared table for offloaded TC eswitch flows')
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reported-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>