x86/amd-iommu: Don't detach device from pt domain on driver unbind

This patch makes sure a device is not detached from the
passthrough domain when the device driver is unloaded or
does otherwise release the device.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

arch/x86/kernel/amd_iommu.c

@@ -1195,6 +1195,8 @@ static int device_change_notifier(struct notifier_block *nb,
 	case BUS_NOTIFY_UNBOUND_DRIVER:
 		if (!domain)
 			goto out;
+		if (iommu_pass_through)
+			break;
 		detach_device(domain, devid);
 		break;
 	case BUS_NOTIFY_ADD_DEVICE: