powerpc/powernv/pci: Sprinkle around some WARN_ON()s

pnv_pci_ioda_configure_bus() should now only ever be called when a device is
added to the bus so add a WARN_ON() to the empty bus check. Similarly,
pnv_pci_ioda_setup_bus_PE() should only ever be called for an unconfigured PE,
so add a WARN_ON() for that case too.
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200417073508.30356-5-oohall@gmail.com

arch/powerpc/platforms/powernv/pci-ioda.c

@@ -1139,7 +1139,7 @@ static struct pnv_ioda_pe *pnv_ioda_setup_bus_PE(struct pci_bus *bus, bool all)
 	 * We should reuse it instead of allocating a new one.
 	 */
 	pe_num = phb->ioda.pe_rmap[bus->number << 8];
-	if (pe_num != IODA_INVALID_PE) {
+	if (WARN_ON(pe_num != IODA_INVALID_PE)) {
 		pe = &phb->ioda.pe_array[pe_num];
 		return NULL;
 	}
@@ -3199,7 +3199,7 @@ static void pnv_pci_configure_bus(struct pci_bus *bus)
 	dev_info(&bus->dev, "Configuring PE for bus\n");
 
 	/* Don't assign PE to PCI bus, which doesn't have subordinate devices */
-	if (list_empty(&bus->devices))
+	if (WARN_ON(list_empty(&bus->devices)))
 		return;
 
 	/* Reserve PEs according to used M64 resources */