CONFIG_MACH_APX4DEVKIT is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_MACH_APX4DEVKIT.
Result is shown for kernelversion 5.3.7

Support Bluegiga APX4 Development Kit

modulename: mach-apx4devkit.ko

configname: CONFIG_MACH_APX4DEVKIT

Linux Kernel Configuration
└─>Support Bluegiga APX4 Development Kit
In linux kernel since version 3.4 (release Date: 2012-05-20)  
source code:
arch/arm/mach-mxs/mach-apx4devkit.c

depends
CONFIG_ARCH_MXS