CONFIG_MACH_MX53_LOCO is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Support MX53 LOCO platforms

modulename: board-mx53_loco.ko

configname: CONFIG_MACH_MX53_LOCO

Linux Kernel Configuration
└─>Support MX53 LOCO platforms
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
Include support for MX53 LOCO platform. This includes specific
configurations for the board and its peripherals.

source code:
arch/arm/mach-mx5/board-mx53_loco.c