CONFIG_PPC is not available for thedefaultarchitecture x86.
Result is shown for architecture ppc

CONFIG_PPC (not configurable)

modulename: setup-bus.ko

configname: CONFIG_PPC

Linux/PowerPC Kernel Configuration
└─>PPC
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
source code:
drivers/pci/setup-bus.c