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

mackerel board

modulename: board-mackerel.ko

configname: CONFIG_MACH_MACKEREL

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