net/mlx5e: Create q counters on uplink representors

Q counters were disabled for all types of representors to prevent an issue
where there is not enough resources to init q counters for 127 representor
instances. Enable q counters only for uplink representors to support
"rx_out_of_buffer", "rx_if_down_packets" counters in ethtool.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>