CONFIG_SOC_AU1550 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_SOC_AU1550 (not configurable)

modulename: fixup-au1000.ko

configname: CONFIG_SOC_AU1550

Linux/MIPS Kernel Configuration
└─>SOC_AU1550
In linux kernel since version 2.6.12  
source code:
arch/mips/pci/

is selected by
CONFIG_SOUND_AU1550_AC97