iommu/vt-d: correct flush_unmaps pfn usage

Change flush_unmaps() to correctly pass iommu_flush_iotlb_psi()
dma addresses.  (x86_64 mm and dma have the same size for pages
at the moment, but this usage improves consistency.)
Signed-off-by: Omer Peleg <omer@cs.technion.ac.il>
[mad@cs.technion.ac.il: rebased and reworded the commit message]
Signed-off-by: Adam Morrison <mad@cs.technion.ac.il>
Reviewed-by: Shaohua Li <shli@fb.com>
Reviewed-by: Ben Serebrin <serebrin@google.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/iommu/intel-iommu.c

@@ -3548,7 +3548,8 @@ static void flush_unmaps(struct deferred_flush_data *flush_data)
 			/* On real hardware multiple invalidations are expensive */
 			if (cap_caching_mode(iommu->cap))
 				iommu_flush_iotlb_psi(iommu, domain,
-					iova->pfn_lo, iova_size(iova),
+					mm_to_dma_pfn(iova->pfn_lo),
+					mm_to_dma_pfn(iova_size(iova)),
 					!freelist, 0);
 			else {
 				mask = ilog2(mm_to_dma_pfn(iova_size(iova)));