CONFIG_MACH_ECBAT91 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

emQbit ECB_AT91 SBC

modulename: board-ecbat91.ko

configname: CONFIG_MACH_ECBAT91

Linux Kernel Configuration
└─>Atmel AT91 System-on-Chip
└─>emQbit ECB_AT91 SBC
In linux kernel since version 2.6.26 (release Date: 2008-07-13)  
Select this if you are using emQbit's ECB_AT91 board.
<http://wiki.emqbit.com/free-ecb-at91>

source code:
arch/arm/mach-at91/board-ecbat91.c