pci: Support absence of base location code
pci: Support absence of base location code

We support having no base location code in the PHB. In that case we
only use the slot label, if it exists, to create the location code.

This allows us to support simpler loc codes for OpenPower.

Signed-off-by: Benjamin Herrenschmidt <a7089bb6e7e92505d88aaff006cbdd60cc9120b6@kernel.crashing.org>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

qemu/skiboot,qemu/skiboot,csmart/skiboot,open-power/skiboot,mikey/skiboot,shenki/skiboot,apopple/skiboot,mikey/skiboot,shenki/skiboot,open-power/skiboot,stewart-ibm/skiboot,open-power/skiboot,legoater/skiboot,qemu/skiboot,mikey/skiboot,shenki/skiboot,stewart-ibm/skiboot,legoater/skiboot,open-power/skiboot,shenki/skiboot,csmart/skiboot,stewart-ibm/skiboot,qemu/skiboot,apopple/skiboot,legoater/skiboot,open-power/skiboot,apopple/skiboot,qemu/skiboot,csmart/skiboot,legoater/skiboot,legoater/skiboot,shenki/skiboot