CONFIG_ARCH_AT91X40 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
ARM7 AT91X40
modulename: at91x40.ko
configname: CONFIG_ARCH_AT91X40
Core type
└─>ARM7 AT91X40
In linux kernel since version 2.6.24 (release Date: 2008-01-24)
Select this if you are using one of Atmel's AT91X40 SoC.