default or selected kernelversion does not have config value CONFIG_ARM_ARMADA_370_XP_CPUIDLE.
Result is shown for kernelversion 5.4.123

CPU Idle Driver for Armada 370/XP family processors

modulename: cpuidle-armada-370-xp.ko

configname: CONFIG_ARM_ARMADA_370_XP_CPUIDLE

Linux Kernel Configuration
└─>CPU Idle Driver for Armada 370/XP family processors
In linux kernel since version 3.16 (release Date: 2014-08-03)  
Select this to enable cpuidle on Armada 370/XP processors.

source code:
drivers/cpuidle/cpuidle-armada-370-xp.c