CONFIG_ATH79_DEV_GPIO_BUTTONS is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_ATH79_DEV_GPIO_BUTTONS (not configurable)

modulename: dev-gpio-buttons.ko

configname: CONFIG_ATH79_DEV_GPIO_BUTTONS

Linux Kernel Configuration
└─>ATH79_DEV_GPIO_BUTTONS
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
source code:
arch/mips/ath79/dev-gpio-buttons.c
depends
CONFIG_ATH79