CONFIG_PPC_83xx is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Freescale 83xx

configname: CONFIG_PPC_83xx

Processor Type
└─>Freescale 83xx
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  

depends
 or CONFIG_6xx or CONFIG_PPC_BOOK3S_32