staging: ncpfs: delete it

The ncpfs code moved into the staging tree back in November 2017 and no
one has complained or even noticed it was gone.  Because of that, let's
just delete it.

Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>