lrdp-v2: support for arm_smmu_domain container of iommu_domain

The arm_smmu_domain is no longer stored in the iommu_domain priv
field, from kernel version 4.1 the arm_smmu_domain is a container
of iommu_domain.

Add support for this configuration.

CRs-Fixed: 1034128
Change-Id: I949ec4a24a7dedc394aedc3e6e30e64f34ca3715