CONFIG_BCM63XX is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

Broadcom BCM63XX based boards

modulename: pci-bcm63xx.ko

configname: CONFIG_BCM63XX

System type
└─>Broadcom BCM63XX based boards
In linux kernel since version 2.6.32 (release Date: 2009-12-02)  
Support for BCM63XX based boards

source code:
arch/mips/pci/

is selected by
CONFIG_SERIAL_BCM63XX