iommu/arm-smmu-v3: Add a type for the CD entry

iommu/arm-smmu-v3: Add a type for the CD entry

Instead of passing a naked __le16 * around to represent a CD table entry
wrap it in a "struct arm_smmu_cd" with an array of the correct size. This
makes it much clearer which functions will comprise the "CD API".

Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Reviewed-by: Michael Shavit <mshavit@google.com>
Reviewed-by: Moritz Fischer <moritzf@google.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/5-v6-228e7adf25eb+4155-smmuv3_newapi_p2_jgg@nvidia.com
Signed-off-by: Will Deacon <will@kernel.org>