CONFIG_ATH79_DEV_AR913X_WMAC is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_ATH79_DEV_AR913X_WMAC (not configurable)

modulename: dev-ar913x-wmac.ko

configname: CONFIG_ATH79_DEV_AR913X_WMAC

Linux Kernel Configuration
└─>ATH79_DEV_AR913X_WMAC
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
source code:
arch/mips/ath79/dev-ar913x-wmac.c

is depended by
CONFIG_ATH79_MACH_AP81