lrdp-v2: Refine AARCH64 page table format parsing

Presently, we can have combination of legacy msm_iommu
or arm-smmu driver managed iommu domain. Further the page
table format also may differ in these respective managed
domains. While with arm-smmu driver, we only use armv8
page table format, with legacy msm_iommu driver we can
support both armv7s and armv8 format page tables.

Refactor the code to distinguish respective domain as to
what pagetable format it supports and accordingly call
corresponding page table parser.

Change-Id: I71479dc70d93124603f6bd5403296efa4e6dfdeb