net/mlx5e: CT: Fix ct debugfs folder name

Need to use sprintf to build a string instead of sscanf. Otherwise
dirname is null and both "ct_nic" and "ct_fdb" won't be created.
But its redundant anyway as driver could be in switchdev mode but
still add nic rules. So use "ct" as folder name.

Fixes: 77422a8f ("net/mlx5e: CT: Add ct driver counters")
Signed-off-by: Chris Mi <cmi@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>