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

Build Kernel with Prefixed Instructions

configname: CONFIG_PPC_KERNEL_PREFIXED

Linux Kernel Configuration
└─>Processor support
└─>Build Kernel with Prefixed Instructions
In linux kernel since version 6.4 (release Date: 2023-06-25)  
POWER10 and later CPUs support prefixed instructions, 8 byte
instructions that include large immediate, pc relative addressing,
and various floating point, vector, MMA.

This option builds the kernel with prefixed instructions, and
allows a pc relative addressing option to be selected.

Kernel support for prefixed instructions in applications and guests
is not affected by this option.