iommu/dma: add missing support for DMA_ATTR_MMIO for dma_iova_unlink()

Commit c288d657dd51 added support for DMA_ATTR_MMIO attribute in the
dma_iova_link() code path, but missed that the CPU cache is being also
touched in the dma_iova_unlink() path. Fix this.

Fixes: c288d657dd51 ("iommu/dma: implement DMA_ATTR_MMIO for dma_iova_link().")
Signed-off-by: Marek Szyprowski <[e-mail]>
Reviewed-by: Jason Gunthorpe <[e-mail]>
Reviewed-by: Leon Romanovsky <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/iommu/dma-iommu.c

···
 			end - addr, iovad->granule - iova_start_pad);
 
 		if (!dev_is_dma_coherent(dev) &&
-		    !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+		    !(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_MMIO)))
 			arch_sync_dma_for_cpu(phys, len, dir);
 
 		swiotlb_tbl_unmap_single(dev, phys, len, dir, attrs);
···
 	size_t unmapped;
 
 	if ((state->__size & DMA_IOVA_USE_SWIOTLB) ||
-	    (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)))
+	    (!dev_is_dma_coherent(dev) &&
+	     !(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_MMIO))))
 		iommu_dma_iova_unlink_range_slow(dev, addr, size, dir, attrs);
 
 	iommu_iotlb_gather_init(&iotlb_gather);