swiotlb-xen: pass dev_addr to swiotlb_tbl_unmap_single

Need to pass the pointer within the swiotlb internal buffer to the
swiotlb library, that in the case of xen_unmap_single is dev_addr, not
paddr.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CC: stable@vger.kernel.org

drivers/xen/swiotlb-xen.c

@@ -451,7 +451,7 @@ static void xen_unmap_single(struct device *hwdev, dma_addr_t dev_addr,
 
 	/* NOTE: We use dev_addr here, not paddr! */
 	if (is_xen_swiotlb_buffer(dev_addr)) {
-		swiotlb_tbl_unmap_single(hwdev, paddr, size, dir);
+		swiotlb_tbl_unmap_single(hwdev, dev_addr, size, dir);
 		return;
 	}