CONFIG_PPC_85xx is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Freescale 85xx

modulename: idle_85xx.ko

and/or

head_85xx.ko

configname: CONFIG_PPC_85xx

Processor Type
└─>Freescale 85xx
In linux kernel since version 2.6.17 (release Date: 2006-06-17)  
source code:
arch/powerpc/kernel/
selects
CONFIG_PPC_E500