CONFIG_CPU_BMIPS4380 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

BMIPS4380

configname: CONFIG_CPU_BMIPS4380

CPU type
└─>BMIPS4380
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
Broadcom BMIPS4380 processors.