CONFIG_PHYS48_TO_HT40 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips
default or selected kernelversion does not have config value CONFIG_PHYS48_TO_HT40.
Result is shown for kernelversion 6.7-rc3

CONFIG_PHYS48_TO_HT40 (not configurable)

configname: CONFIG_PHYS48_TO_HT40

Linux Kernel Configuration
└─>PHYS48_TO_HT40
In linux kernel since version 3.19 (release Date: 2015-02-08)