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

CONFIG_S3C2412_PM_SLEEP (not configurable)

modulename: sleep-s3c2412.ko

and/or

sleep.ko

configname: CONFIG_S3C2412_PM_SLEEP

Linux Kernel Configuration
└─>SAMSUNG S3C24XX SoCs Support
└─>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 such as S3C2416 with similar
sleep procedure.

source code:
/arch/arm/mach-s3c24xx/