arm64: mm: dma-mapping: fix __iommu_alloc_atomic()

arm64: mm: dma-mapping: fix __iommu_alloc_atomic()

__iommu_alloc_atomic() by accident passes a "struct page **pages" pointer
where the pointed memory contains only one valid "struct page *page" to
__iommu_create_mapping(). This ends up with mapping failure at the second
page in ___iommu_create_mapping()->iommu_map().

This commit fixes the issue by calling __iommu_get_pages() in
__iommu_alloc_atomic() to retrieve valid "struct page **pages" pointer from
&atomic_pool->pages[].

bug 200102712

Change-Id: Iae1796b505c4ea66f5a77463f5a49bc0e72a1424
Signed-off-by: JC Kuo <jckuo@nvidia.com>
Reviewed-on: http://git-master/r/739101
Reviewed-by: Krishna Reddy <vdumpa@nvidia.com>