The newly added DMA_ATTR_PRIVILEGED is useful for creating mappings that
are only accessible to privileged DMA engines. Implement it in
dma-iommu.c so that the ARM64 DMA IOMMU mapper can make use of it.
Reviewed-by: Robin Murphy <robin.murphy@arm.com> Tested-by: Robin Murphy <robin.murphy@arm.com> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org> Signed-off-by: Will Deacon <will.deacon@arm.com>