net/mlx5e: mlx5_tc_ct_init does not fail

mlx5_tc_ct_init() either returns a valid pointer or a NULL, either way
the caller can continue, remove IS_ERR check from callers as it has no
effect.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>