CONFIG_MACH_AG5EVM is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

AG5EVM board

modulename: board-ag5evm.ko

configname: CONFIG_MACH_AG5EVM

Linux Kernel Configuration
└─>AG5EVM board
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
source code:
arch/arm/mach-shmobile/board-ag5evm.c