CONFIG_ARCH_MX31 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_ARCH_MX31.
Result is shown for kernelversion 6.2.5

CONFIG_ARCH_MX31 (not configurable)

configname: CONFIG_ARCH_MX31

Linux Kernel Configuration
└─>ARCH_MX31
In linux kernel since version 2.6.30 (release Date: 2009-06-09)  
is depended by
CONFIG_SOC_IMX31