s390/pci: return error after failed pci ops

Access to pci config space via pci_ops should not fail silently.
Reviewed-by: NGerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: NSebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/pci/pci.c

@@ -405,20 +405,28 @@ static int pci_read(struct pci_bus *bus, unsigned int devfn, int where,
 		    int size, u32 *val)
 {
 	struct zpci_dev *zdev = get_zdev_by_bus(bus);
+	int ret;
 
 	if (!zdev || devfn != ZPCI_DEVFN)
-		return 0;
-	return zpci_cfg_load(zdev, where, val, size);
+		ret = -ENODEV;
+	else
+		ret = zpci_cfg_load(zdev, where, val, size);
+
+	return ret;
 }
 
 static int pci_write(struct pci_bus *bus, unsigned int devfn, int where,
 		     int size, u32 val)
 {
 	struct zpci_dev *zdev = get_zdev_by_bus(bus);
+	int ret;
 
 	if (!zdev || devfn != ZPCI_DEVFN)
-		return 0;
-	return zpci_cfg_store(zdev, where, val, size);
+		ret = -ENODEV;
+	else
+		ret = zpci_cfg_store(zdev, where, val, size);
+
+	return ret;
 }
 
 static struct pci_ops pci_root_ops = {