swiotlb: fix map_sg failure handling

sg list elements might not be continuous.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

lib/swiotlb.c

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index c419ecf..752fd95 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -696,7 +696,7 @@
 				/* Don't panic here, we expect map_sg users
 				   to do proper error handling. */
 				swiotlb_full(hwdev, sg->length, dir, 0);
-				swiotlb_unmap_sg(hwdev, sg - i, i, dir);
+				swiotlb_unmap_sg(hwdev, sgl, i, dir);
 				sgl[0].dma_length = 0;
 				return 0;
 			}