net/mlx5e: IPsec, Remove unnecessary config flag usage

MLX5_IPSEC_DEV() is always defined, no need to protect it under config
flag CONFIG_MLX5_EN_IPSEC, especially in slow path.

Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Raed Salem <raeds@nvidia.com>
Reviewed-by: Huy Nguyen <huyn@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>