CONFIG_BDI_SWITCH is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Include BDI-2000 user context switcher

configname: CONFIG_BDI_SWITCH

Linux Kernel Configuration
└─>Include BDI-2000 user context switcher
In linux kernel since version 2.6.17 (release Date: 2006-06-17)  
Include in-kernel support for the Abatron BDI2000 debugger.
Unless you are intending to debug the kernel with one of these
machines, say N here.