CONFIG_CPU_S5P6450 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_CPU_S5P6450 (not configurable)

modulename: clock-s5p6450.ko

configname: CONFIG_CPU_S5P6450

Linux Kernel Configuration
└─>CPU_S5P6450
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
Enable S5P6450 CPU support

source code: