ARM: dma: add new fields to dma_iommu_mapping

ARM: dma: add new fields to dma_iommu_mapping

Add num_prefetch_page and gap_page.
if selected, prefetch/gap pages will be added for every dma
mapping request.

Also define alignment per mapping. This alignment will be used
to allocate/free iova during dma map/unmap requests.

Bug 1463797

Change-Id: I32b22930b4414e43223287a2555ec50fe3f4ce36
Signed-off-by: Sri Krishna chowdary <schowdary@nvidia.com>
Reviewed-on: http://git-master/r/413266
Reviewed-by: Hiroshi Doyu <hdoyu@nvidia.com>
Tested-by: Hiroshi Doyu <hdoyu@nvidia.com>