CONFIG_S3C_DEV_I2C5 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_S3C_DEV_I2C5 (not configurable)

configname: CONFIG_S3C_DEV_I2C5

Linux Kernel Configuration
└─>S3C_DEV_I2C5
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
Compile in platform device definition for I2C controller 5