CONFIG_CPU_R4300 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

R4300

modulename: c-r4k.ko

and/or

dump_tlb.ko

and/or

r4k_fpu.ko

configname: CONFIG_CPU_R4300

CPU type
└─>R4300
In linux kernel since version 2.6.12  
MIPS Technologies R4300-series processors.

source code:
arch/mips/mm/