CONFIG_ARM is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_ARM (not configurable)

modulename: setup-bus.ko

configname: CONFIG_ARM

Linux Kernel Configuration
└─>ARM
In linux kernel since version 2.6.12  
The ARM series is a line of low-power-consumption RISC chip designs
licensed by ARM Ltd and targeted at embedded applications and
handhelds such as the Compaq IPAQ. ARM-based PCs are no longer
manufactured, but legacy ARM-based PC hardware remains popular in
Europe. There is an ARM Linux project with a web page at
<http://www.arm.linux.org.uk/>.

source code:
drivers/pci/