CONFIG_CPU_S5P6440 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_CPU_S5P6440 (not configurable)

modulename: cpu.ko

and/or

setup-i2c0.ko

configname: CONFIG_CPU_S5P6440

Linux Kernel Configuration
└─>CPU_S5P6440
In linux kernel since version 2.6.34 (release Date: 2010-05-16)  
Enable S5P6440 CPU support

source code:
/arch/arm/mach-s5p6440/


is selected by
CONFIG_SERIAL_S3C6400

is depended by
CONFIG_MACH_SMDK6440