net/mlx5e: Disable hw-tc-offload when MLX5_CLS_ACT config is disabled

The cited commit introduce new CONFIG_MLX5_CLS_ACT kconfig variable
to control compilation of TC hardware offloads implementation.
When this configuration is disabled the driver is still wrongly
reports in ethtool that hw-tc-offload is supported.

Fixed by reporting hw-tc-offload is supported only when
CONFIG_MLX5_CLS_ACT is enabled.

Fixes: d956873f

 ("net/mlx5e: Introduce kconfig var for TC support")
Signed-off-by: Maor Dickman <maord@nvidia.com>
Reviewed-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>