CONFIG_ARCH_MX31 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_ARCH_MX31 (not configurable)

modulename: clock-imx31.ko

configname: CONFIG_ARCH_MX31

Linux Kernel Configuration
└─>ARCH_MX31
In linux kernel since version 2.6.30 (release Date: 2009-06-09)  
source code: