net/mlx5: Remove MLX5E_LOCKED_FLOW flag

The MLX5E_LOCKED_FLOW flag is not checked anywhere now so remove it
entirely.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>