CONFIG_BCM47XX is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

BCM47XX based boards

modulename: pci-bcm47xx.ko

and/or

configname: CONFIG_BCM47XX

System type
└─>BCM47XX based boards
In linux kernel since version 2.6.24 (release Date: 2008-01-24)  
Support for BCM47XX based boards


is selected by
CONFIG_BGMAC_BCMA