s390/pci: Do not disable PF when VFs exist

The Physical function should not be disabled until no virtual
functions depends on it.
Let's force the user to first use echo 0 > sriov_numfs before
allowing to disable the PF with echo 0 > power.
Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

drivers/pci/hotplug/s390_pci_hpc.c

@@ -91,6 +91,9 @@ static int disable_slot(struct hotplug_slot *hotplug_slot)
 
 	pdev = pci_get_slot(zbus->bus, zdev->devfn);
 	if (pdev) {
+		if (pci_num_vf(pdev))
+			return -EBUSY;
+
 		pci_stop_and_remove_bus_device_locked(pdev);
 		pci_dev_put(pdev);
 	}