CONFIG_ARCH_MX53 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_ARCH_MX53 (not configurable)

configname: CONFIG_ARCH_MX53

Linux Kernel Configuration
└─>ARCH_MX53
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
is depended by
CONFIG_SOC_IMX53