CONFIG_ATH79_DEV_SPI is not available for thedefaultarchitecture x86.
Result is shown for architecture mips
default or selected kernelversion does not have config value CONFIG_ATH79_DEV_SPI.
Result is shown for kernelversion 6.9.9

CONFIG_ATH79_DEV_SPI (not configurable)

configname: CONFIG_ATH79_DEV_SPI

Linux Kernel Configuration
└─>ATH79_DEV_SPI
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
depends
CONFIG_ATH79