CONFIG_SOC_AU1200 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_SOC_AU1200 (not configurable)

configname: CONFIG_SOC_AU1200

Linux/MIPS Kernel Configuration
└─>SOC_AU1200
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  

is selected by
CONFIG_FB_AU1200