iommu/arm-smmu-v3: Add types for each level of the 2 level stream table

Add types struct arm_smmu_strtab_l1 and l2 to represent the HW layout of
the descriptors, and use them in most places, following patches will get
the remaing places. The size of the l1 and l2 HW allocations are
sizeof(struct arm_smmu_strtab_l1/2).

This provides some more clarity than having raw __le64 *'s and sizes
computed via macros.

Remove STRTAB_L1_DESC_DWORDS.

Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/2-v4-6416877274e1+1af-smmuv3_tidy_jgg@nvidia.com


Signed-off-by: Will Deacon <will@kernel.org>