CONFIG_S3C_GPIO_CFG_S3C64XX is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_S3C_GPIO_CFG_S3C64XX (not configurable)

configname: CONFIG_S3C_GPIO_CFG_S3C64XX

Linux Kernel Configuration
└─>S3C_GPIO_CFG_S3C64XX
In linux kernel since version 2.6.29 (release Date: 2009-03-23)  
Internal configuration to enable S3C64XX style GPIO configuration
functions.

depends
CONFIG_PLAT_S3C

is depended by
CONFIG_PLAT_S3C64XX