iommu/arm-smmu: Implement iommu_ops->def_domain_type call-back

Implement the new def_domain_type call-back for the ARM
SMMU driver. We need this to support requesting the domain
type by the client devices.

Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/28c5d101cc4ac29aff3553ecec7cf256d0907ed7.1587407458.git.saiprakash.ranjan@codeaurora.org
Signed-off-by: Will Deacon <will@kernel.org>