CONFIG_M525x is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k

MCF525x

modulename: m525x.ko

configname: CONFIG_M525x

Linux Kernel Configuration
└─>MCF525x
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Freescale (Motorola) Coldfire 5251/5253 processor support.

source code:
arch/m68k/coldfire/