CONFIG_ARCH_S5P64X0 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Samsung S5P6440 S5P6450

configname: CONFIG_ARCH_S5P64X0

ARM system type
└─>Samsung S5P6440 S5P6450
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
Samsung S5P64X0 CPU based systems, such as the Samsung SMDK6440,
SMDK6450.


is selected by
CONFIG_FB_S3C