CONFIG_ARCH_MX25 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_ARCH_MX25.
Result is shown for kernelversion 6.5.1

CONFIG_ARCH_MX25 (not configurable)

configname: CONFIG_ARCH_MX25

Linux Kernel Configuration
└─>Freescale i.MX support
└─>ARCH_MX25
In linux kernel since version 2.6.32 (release Date: 2009-12-02)  
depends
CONFIG_ARCH_MXC

is depended by
CONFIG_SOC_IMX25