default or selected kernelversion does not have config value CONFIG_STAGING_RDMA.
Result is shown for kernelversion 5.4.229

RDMA staging drivers

configname: CONFIG_STAGING_RDMA

Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>InfiniBand support
└─>RDMA staging drivers
In linux kernel since version 4.3 (release Date: 2015-11-01)  
This option allows you to select a number of RDMA drivers that
fall into one of two categories: deprecated drivers being held
here before finally being removed or new drivers that still need
some work before being moved to the normal RDMA driver area.

If you wish to work on these drivers, to help improve them, or
to report problems you have with them, please use the
linux-rdma@vger.kernel.org mailing list.

If in doubt, say N here.