CONFIG_S5P_PM is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_S5P_PM (not configurable)

modulename: s5p-pm.ko

configname: CONFIG_S5P_PM

Linux Kernel Configuration
└─>S5P_PM
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Common code for power management support on S5P and newer SoCs
Note: Do not select this for S5P6440 and S5P6450.

source code:
/arch/arm/plat-samsung/