default or selected kernelversion does not have config value CONFIG_ANDROID_PERSISTENT_RAM.
Result is shown for kernelversion 5.3.7

CONFIG_ANDROID_PERSISTENT_RAM (not configurable)

modulename: persistent_ram.ko

configname: CONFIG_ANDROID_PERSISTENT_RAM

Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>Android
└─>ANDROID_PERSISTENT_RAM
In linux kernel since version 3.4 (release Date: 2012-05-20)  
source code:
drivers/staging/android/persistent_ram.c