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

VSX Support

configname: CONFIG_VSX

Linux Kernel Configuration
└─>Processor support
└─>VSX Support
In linux kernel since version 2.6.27 (release Date: 2008-10-09)  
This option enables kernel support for the Vector Scaler extensions
to the PowerPC processor. The kernel currently supports saving and
restoring VSX registers, and turning on the 'VSX enable' bit so user
processes can execute VSX instructions.

This option is only useful if you have a processor that supports
VSX (P7 and above), but does not have any affect on a non-VSX
CPUs (it does, however add code to the kernel).

If in doubt, say Y here.