default or selected kernelversion does not have config value CONFIG_ANDROID_PMEM.
Result is shown for kernelversion 5.16-rc3

Android pmem allocator

modulename: pmem.ko

configname: CONFIG_ANDROID_PMEM

Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>Android
└─>Android pmem allocator
In linux kernel since version 3.3.1 (release Date: 2012-04-02)  
source code:
drivers/staging/android/pmem.c