CONFIG_M54xx is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k

CONFIG_M54xx (not configurable)

modulename: m54xx.ko

configname: CONFIG_M54xx

Linux Kernel Configuration
└─>M54xx
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
source code:
arch/m68k/coldfire/
depends
CONFIG_COLDFIRE

is depended by
CONFIG_M547x
CONFIG_M548x