CONFIG_BF542 is not available for thedefaultarchitecture x86.
Result is shown for architecture blackfin

BF542

configname: CONFIG_BF542

CPU
└─>BF542
In linux kernel since version 2.6.24 (release Date: 2008-01-24)  
BF542 Processor Support.

depends
 or CONFIG_BF542M or CONFIG_BF542_std