CONFIG_LEON_PCI is not available for thedefaultarchitecture x86.
Result is shown for architecture sparc

CONFIG_LEON_PCI (not configurable)

modulename: leon_pci.ko

configname: CONFIG_LEON_PCI

Linux Kernel Configuration
└─>Bus options (PCI etc.)
└─>LEON_PCI
In linux kernel since version 3 (release Date: 2011-07-21)  
source code:
arch/sparc/kernel/leon_pci.c