iommu: add ARM LPAE page table allocator

A number of IOMMUs found in ARM SoCs can walk architecture-compatible
page tables.

This patch adds a generic allocator for Stage-1 and Stage-2 v7/v8
long-descriptor page tables. 4k, 16k and 64k pages are supported, with
up to 4-levels of walk to cover a 48-bit address space.

Change-Id: I32740cfa795c55e0d3683b42105b4f49c9dcf984
Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Git-commit: e1d3c0fd701df831169b116cd5c5d6203ac07f70
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


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