CONFIG_PCI_XILINX is not available for thedefaultarchitecture x86.
Result is shown for architecture microblaze

Xilinx PCI host bridge support

modulename: xilinx_pci.ko

configname: CONFIG_PCI_XILINX

Linux Kernel Configuration
└─>Bus Options
└─>Xilinx PCI host bridge support
In linux kernel since version 2.6.34 (release Date: 2010-05-16)  
source code:
arch/microblaze/pci/xilinx_pci.c
depends
CONFIG_PCI