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.

Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 3faaa41..306454f 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -19,6 +19,15 @@
 config IOMMU_IO_PGTABLE
 	bool
 
+config IOMMU_IO_PGTABLE_LPAE
+	bool "ARMv7/v8 Long Descriptor Format"
+	select IOMMU_IO_PGTABLE
+	help
+	  Enable support for the ARM long descriptor pagetable format.
+	  This allocator supports 4K/2M/1G, 16K/32M and 64K/512M page
+	  sizes at both stage-1 and stage-2, as well as address spaces
+	  up to 48-bits in size.
+
 endmenu
 
 config OF_IOMMU