net/mlx5: Use aligned variable while allocating ICM memory

The alignment value is part of the input structure, so use it and spare
extra memory allocation when is not needed.
Now, using the new ability when allocating icm for Direct-Rule
insertion.
Signed-off-by: Ariel Levkovich <lariel@mellanox.com>
Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>