staging: drop kpc2000 driver

It seems that the old developer is no longer with the company producing
this device, and the company has no plans on getting this out of the
staging directory at all, so let's drop the driver for now as it's
pretty much abandonded.

If someone want to support this and get it out of staging, we can easily
revert this change and bring it back.

Cc: Matt Sickler <matt.sickler@msk4.com>
Link: https://lore.kernel.org/r/20210610183153.2397760-1-gregkh@linuxfoundation.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>