CONFIG_M525x is not available for the selected architecture x86.
Result is shown for architecture m68k
MCF525x
modulename: m525x.ko
configname: CONFIG_M525x
ColdFire SoC type
└─>MCF525x
In linux kernel since version 3.1 (release Date: 2011-10-24)
Freescale (Motorola) Coldfire 5251/5253 processor support.