net/mlx5: crypto, Fix wrong offset in encryption key command

Fix the 128b key offset in key encryption key creation command,
per the HW specification.

Fixes: 45d3b55d

 ("net/mlx5: Add crypto library to support create/destroy encryption key")
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>