CONFIG_ARCH_MVEBU is not available for the selected architecture x86.
Result is shown for architecture arm

Marvell Engineering Business Unit (MVEBU) SoCs

configname: CONFIG_ARCH_MVEBU

Linux Kernel Configuration
└─>Marvell Engineering Business Unit (MVEBU) SoCs
In linux kernel since version 3.1 (release Date: 2011-10-24)