CONFIG_MODULE_APX4 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_MODULE_APX4 (not configurable)

configname: CONFIG_MODULE_APX4

Linux Kernel Configuration
└─>MODULE_APX4
In linux kernel since version 3.4 (release Date: 2012-05-20)  

depends
CONFIG_ARCH_MXS

is depended by
CONFIG_MACH_APX4DEVKIT