Fix pci_add storage not to exit on bad first argument

Monitor command "pci_add ADDR storage ..." does its work in
qemu_pci_hot_add_nic().  It called pci_create(..., ADDR) to create the
device.  That's wrong, because pci_create() terminates the program
when ADDR is invalid.

Use pci_get_bus_devfn() and pci_create_noinit() instead.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/hw/pci.c b/hw/pci.c
index e2f88ff..aebe0c5 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -317,7 +317,7 @@
     return 0;
 }
 
-static PCIBus *pci_get_bus_devfn(int *devfnp, const char *devaddr)
+PCIBus *pci_get_bus_devfn(int *devfnp, const char *devaddr)
 {
     int dom, bus;
     unsigned slot;