CONFIG_MIPS is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_MIPS (not configurable)

modulename: setup-bus.ko

configname: CONFIG_MIPS

Linux Kernel Configuration
└─>MIPS
In linux kernel since version 2.6.12  
source code:
drivers/pci/

is selected by
CONFIG_USB_XHCI_MTK