iommu/arm-smmu: make use of generic LPAE allocator

The ARM SMMU can walk LPAE page tables, so make use of the generic
allocator.

Change-Id: I7acd0e6c6e8046a4f0497a8fbdba46986192f83f
Signed-off-by: Will Deacon <will.deacon@arm.com>
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Git-commit: 518f7136244c167538f732691be589959310b295
[mitchelh: merge with our changes to domain locking, non-shareable
 page tables, and pte zero'ing, some of which will need to be added
 back now in the generic allocator code]
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>