default or selected kernelversion does not have config value CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT.
Result is shown for kernelversion 6.9.9

CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT (not configurable)

configname: CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT

Linux Kernel Configuration
└─>General architecture-dependent options
└─>ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
In linux kernel since version 5.1 (release Date: 2019-05-05)  

depends
CONFIG_MMU