net/mlx5e: Fix macsec ASO context alignment

Currently mlx5e_macsec_umr struct does not satisfy hardware memory
alignment requirement. Hence the result of querying advanced steering
operation (ASO) is not copied to the memory region as expected.

Fix by satisfying hardware memory alignment requirement and move
context to be first field in struct for better readability.

Fixes: 1f53da67 ("net/mlx5e: Create advanced steering operation (ASO) object for MACsec")
Signed-off-by: Emeel Hakim <ehakim@nvidia.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>