CONFIG_M520x is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k

MCF520x

modulename: m520x.ko

configname: CONFIG_M520x

ColdFire SoC type
└─>MCF520x
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
Freescale Coldfire 5207/5208 processor support.

source code:
selects
CONFIG_GENERIC_CLOCKEVENTS
CONFIG_HAVE_CACHE_SPLIT

depends
NOT CONFIG_MMU