CONFIG_PPC_OF is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc
default or selected kernelversion does not have config value CONFIG_PPC_OF.
Result is shown for kernelversion 6.5.1

CONFIG_PPC_OF (not configurable)

modulename: of_platform.ko

configname: CONFIG_PPC_OF

Linux Kernel Configuration
└─>PPC_OF
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
source code:
arch/powerpc/kernel/