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

IBM Virtual Accelerator Switchboard (VAS)

modulename: vas.ko

and/or

vas-api.ko

configname: CONFIG_PPC_VAS

Linux Kernel Configuration
└─>IBM Virtual Accelerator Switchboard (VAS)
In linux kernel since version 3.10 (release Date: 2013-06-30)  
This enables support for IBM Virtual Accelerator Switchboard (VAS).

VAS devices are found in POWER9-based and later systems, they
provide access to accelerator coprocessors such as NX-GZIP and
NX-842. This config allows the kernel to use NX-842 accelerators,
and user-mode APIs for the NX-GZIP accelerator on POWER9 PowerNV
and POWER10 PowerVM platforms.

If unsure, say "N".

source code: