CONFIG_PPC_47x is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Support for 47x variant

configname: CONFIG_PPC_47x

Linux Kernel Configuration
└─>Support for 47x variant
In linux kernel since version 2.6.35 (release Date: 2010-08-01)  
This option enables support for the 47x family of processors and is
not currently compatible with other 44x or 46x varients

selects
CONFIG_MPIC

depends
CONFIG_44x

is selected by
CONFIG_FSP2