CONFIG_CPU_S3C6400_INIT is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_CPU_S3C6400_INIT (not configurable)

modulename: s3c6400-init.ko

configname: CONFIG_CPU_S3C6400_INIT

Linux Kernel Configuration
└─>CPU_S3C6400_INIT
In linux kernel since version 2.6.29 (release Date: 2009-03-23)  
Common initialisation code for the S3C6400 that is shared
by other CPUs in the series, such as the S3C6410.

source code:
arch/arm/plat-s3c64xx/s3c6400-init.c