Remove NINTERFACE define

Remove NINTERFACE define

Whatever behaviour was controlled by the -DNINTERFACE define is long
gone from our code base (git log -SNINTERFACE can't find any references,
which suggests that its removal predates OpenAFS).

Simplify our Makefiles by removing the definition

Change-Id: Ic84261eb40aa7de9b7c0ec7b8372517b09e242d2
Reviewed-on: http://gerrit.openafs.org/4427
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>