CONFIG_MACH_AT91SAM9261EK is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_MACH_AT91SAM9261EK.
Result is shown for kernelversion 6.5.1

Atmel AT91SAM9261-EK Evaluation Kit

modulename: board-sam9261ek.ko

configname: CONFIG_MACH_AT91SAM9261EK

Linux Kernel Configuration
└─>Atmel Non-DT world
└─>Atmel AT91SAM9261-EK Evaluation Kit
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
Select this if you are using Atmel's AT91SAM9261-EK Evaluation Kit.
<http://www.atmel.com/dyn/products/tools_card.asp?tool_id=3820>

source code: