vfio iommu type1: Fix memory leak in vfio_iommu_type1_pin_pages

pfn is not added to pfn_list when vfio_add_to_pfn_list fails.
vfio_unpin_page_external will exit directly without calling
vfio_iova_put_vfio_pfn.  This will lead to a memory leak.

Fixes: a54eb550 ("vfio iommu type1: Add support for mediated devices")
Signed-off-by: Xiaoyang Xu <xuxiaoyang2@huawei.com>
[aw: simplified logic, add Fixes]
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/vfio_iommu_type1.c

@@ -693,7 +693,8 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 
 		ret = vfio_add_to_pfn_list(dma, iova, phys_pfn[i]);
 		if (ret) {
-			vfio_unpin_page_external(dma, iova, do_accounting);
+			if (put_pfn(phys_pfn[i], dma->prot) && do_accounting)
+				vfio_lock_acct(dma, -1, true);
 			goto pin_unwind;
 		}