intel-iommu: Fix get_domain_for_dev() error path

If we run out of domain_ids and fail iommu_attach_domain(), we
fall into domain_exit() without having setup enough of the
domain structure for this to do anything useful.  In fact, it
typically runs off into the weeds walking the bogus domain->devices
list.  Just free the domain.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Donald Dutile <ddutile@redhat.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Cc: stable@kernel.org

drivers/pci/intel-iommu.c

@@ -1835,7 +1835,7 @@ static struct dmar_domain *get_domain_for_dev(struct pci_dev *pdev, int gaw)
 
 	ret = iommu_attach_domain(domain, iommu);
 	if (ret) {
-		domain_exit(domain);
+		free_domain_mem(domain);
 		goto error;
 	}