CONFIG_MACH_BK3 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Support Liebherr BK3.1

configname: CONFIG_MACH_BK3

Linux Kernel Configuration
└─>EP93xx-based
└─>Support Liebherr BK3.1
In linux kernel since version 3.10 (release Date: 2013-06-30)  
Say 'Y' here if you want your kernel to support the
Liebherr controller BK3.1.