Revert "iommu/arm-smmu: implement DOMAIN_ATTR_PT_BASE_ADDR"

This reverts commit c8690d83e1e1b09d55ed75d6776efe42915b9c95 since it
won't compile when arm-smmu.c moves to the generic page table
allocator (since cfg.pgd is being deleted there).  We'll bring this back
in with the appropriate fix once the generic page table allocator patch
is in.

Change-Id: I956d902999a05653e70f7cb7a90ac5010f9926de
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>