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

Broadcom Generic BMIPS kernel

configname: CONFIG_BMIPS_GENERIC

System type
└─>Broadcom Generic BMIPS kernel
In linux kernel since version 3.10 (release Date: 2013-06-30)  
Build a generic DT-based kernel image that boots on select
BCM33xx cable modem chips, BCM63xx DSL chips, and BCM7xxx set-top
box chips. Note that CONFIG_CPU_BIG_ENDIAN/CONFIG_CPU_LITTLE_ENDIAN
must be set appropriately for your board.


is selected by
CONFIG_MTD_BCM63XX_PARTS