CONFIG_CPU_LOONGSON2 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_CPU_LOONGSON2 (not configurable)

modulename: dma.ko

configname: CONFIG_CPU_LOONGSON2

Linux Kernel Configuration
└─>CPU selection
└─>CPU_LOONGSON2
In linux kernel since version 2.6.23 (release Date: 2007-10-09)  
source code:
arch/mips/loongson64/common/dma.c