CONFIG_ARCH_AT91CAP9 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

AT91CAP9

modulename: at91cap9.ko

configname: CONFIG_ARCH_AT91CAP9

Atmel AT91 Processor
└─>AT91CAP9
In linux kernel since version 2.6.25 (release Date: 2008-04-16)  
source code:
/arch/arm/mach-at91/