powerpc/iommu: Update the generic code to use dynamic iommu page sizes

This patch updates the generic iommu backend code to use the
it_page_shift field to determine the iommu page size instead of
using hardcoded values.

Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --cc arch/powerpc/include/asm/iommu.h
Simple merge

diff --cc arch/powerpc/kernel/dma-iommu.c
Simple merge

diff --cc arch/powerpc/kernel/iommu.c
Simple merge

diff --cc arch/powerpc/kernel/vio.c
Simple merge

diff --cc arch/powerpc/platforms/powernv/pci.c
Simple merge

diff --cc drivers/net/ethernet/ibm/ibmveth.c
Simple merge