s390/pci: PCI hotplug support via SCLP

Add SCLP PCI configure/deconfigure and implement a PCI hotplug
controller (s390_pci_hpc). The hotplug controller creates a slot
for every PCI function in stand-by or configured state. The PCI
functions are named after the PCI function ID (fid). By writing to
the power attribute in /sys/bus/pci/slots/<fid>/power the PCI function
is moved to stand-by or configured state. If moved to the configured
state the device is automatically scanned by the s390 PCI layer.

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/pci/hotplug/Kconfig b/drivers/pci/hotplug/Kconfig
index b0e46de..13e9e63 100644
--- a/drivers/pci/hotplug/Kconfig
+++ b/drivers/pci/hotplug/Kconfig
@@ -151,4 +151,15 @@
 
 	  When in doubt, say N.
 
+config HOTPLUG_PCI_S390
+	tristate "System z PCI Hotplug Support"
+	depends on S390 && 64BIT
+	help
+	  Say Y here if you want to use the System z PCI Hotplug
+	  driver for PCI devices. Without this driver it is not
+	  possible to access stand-by PCI functions nor to deconfigure
+	  PCI functions.
+
+	  When in doubt, say Y.
+
 endif # HOTPLUG_PCI