scsi: libsas: Fix error path in sas_notify_lldd_dev_found()

In sas_notify_lldd_dev_found(), if we can't allocate the necessary
resources, then it seems like the wrong thing to mark the device as found
and to increment the reference count.  None of the callers ever drop the
reference in that situation.

[mkp: tweaked commit desc based on feedback from John]

Link: https://lore.kernel.org/r/20200905125836.GF183976@mwanda
Fixes: 735f7d2fed ("[SCSI] libsas: fix domain_device leak")
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Acked-by: John Garry <john.garry@huawei.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/libsas/sas_discover.c

@@ -182,10 +182,11 @@ int sas_notify_lldd_dev_found(struct domain_device *dev)
 		pr_warn("driver on host %s cannot handle device %016llx, error:%d\n",
 			dev_name(sas_ha->dev),
 			SAS_ADDR(dev->sas_addr), res);
+		return res;
 	}
 	set_bit(SAS_DEV_FOUND, &dev->state);
 	kref_get(&dev->kref);
-	return res;
+	return 0;
 }