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

CONFIG_MIPS_GENERIC (not configurable)

configname: CONFIG_MIPS_GENERIC

Linux Kernel Configuration
└─>MIPS_GENERIC
In linux kernel since version 3.10 (release Date: 2013-06-30)  
is selected by
CONFIG_PCH_GBE