CONFIG_PCI_AR724X is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_PCI_AR724X (not configurable)

modulename: pci-ar724x.ko

configname: CONFIG_PCI_AR724X

Linux Kernel Configuration
└─>PCI_AR724X
In linux kernel since version 3.1 (release Date: 2011-10-24)  
source code:
arch/mips/pci/pci-ar724x.c
depends
CONFIG_ATH79