CONFIG_M5271 is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k

MCF5271

configname: CONFIG_M5271

Linux Kernel Configuration
└─>MCF5271
In linux kernel since version 2.6.14 (release Date: 2005-10-27)  
Freescale (Motorola) ColdFire 5270/5271 processor support.