CONFIG_XTENSA_VARIANT_MMU is not available for thedefaultarchitecture x86.
Result is shown for architecture xtensa

Core variant has a Full MMU (TLB, Pages, Protection, etc)

configname: CONFIG_XTENSA_VARIANT_MMU

Linux Kernel Configuration
└─>Processor type and features
└─>Core variant has a Full MMU (TLB, Pages, Protection, etc)
In linux kernel since version 3.17 (release Date: 2014-10-05)  
Build a Conventional Kernel with full MMU support,
ie: it supports a TLB with auto-loading, page protection.