CONFIG_ARCH_BCM_63XX is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Broadcom BCM63xx DSL SoC

configname: CONFIG_ARCH_BCM_63XX

Linux Kernel Configuration
└─>Broadcom SoC Support
└─>Broadcom BCM63xx DSL SoC
In linux kernel since version 3.10 (release Date: 2013-06-30)  
This enables support for systems based on Broadcom DSL SoCs.
It currently supports the 'BCM63XX' ARM-based family, which includes
the BCM63138 variant.