CONFIG_MACH_AT91RM9200EK is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Atmel AT91RM9200-EK Evaluation Kit

modulename: board-ek.ko

configname: CONFIG_MACH_AT91RM9200EK

Linux Kernel Configuration
└─>Atmel AT91 System-on-Chip
└─>Atmel AT91RM9200-EK Evaluation Kit
In linux kernel since version 2.6.16 (release Date: 2006-03-19)  
Select this if you are using Atmel's AT91RM9200-EK Evaluation Kit.
<http://www.atmel.com/dyn/products/tools_card.asp?tool_id=3507>

source code: