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

Genmai board

modulename: board-genmai-reference.ko

and/or

board-genmai.ko

configname: CONFIG_MACH_GENMAI

Linux Kernel Configuration
└─>Renesas ARM SoCs
└─>Genmai board
In linux kernel since version 3.13 (release Date: 2014-01-19)  
source code:
arch/arm/mach-shmobile/board-genmai-reference.c
selects
CONFIG_USE_OF