CONFIG_CPU_MIPS64_R2 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

MIPS64 Release 2

configname: CONFIG_CPU_MIPS64_R2

CPU type
└─>MIPS64 Release 2
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
Choose this option to build a kernel for release 2 or later of the
MIPS64 architecture. Many modern embedded systems with a 64-bit
MIPS processor are based on a MIPS64 processor. If you know the
specific type of processor in your system, choose those that one
otherwise CPU_MIPS64_R1 is a safe bet for any MIPS64 system.