CONFIG_CPU_MIPSR2 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_CPU_MIPSR2 (not configurable)

configname: CONFIG_CPU_MIPSR2

Linux Kernel Configuration
└─>CPU_MIPSR2
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  

is depended by
CONFIG_CPU_LOONGSON64