CONFIG_S3C2412_PM_SLEEP is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_S3C2412_PM_SLEEP (not configurable)

modulename: sleep.ko

and/or

sleep-s3c2412.ko

configname: CONFIG_S3C2412_PM_SLEEP

Linux Kernel Configuration
└─>S3C2412_PM_SLEEP
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
Internal config node to apply sleep for S3C2412 power management.
Can be selected by another SoCs with similar sleep procedure.

source code: