[GFS2] Fix Kconfig

Here is a patch to fix up the Kconfig so that we don't land up with
problems when people disable the NET subsystem.  Thanks for all the hints and
suggestions that people have sent me regarding this.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Aleksandr Koltsoff <czr@iki.fi>
Cc: Toralf Förster <toralf.foerster@gmx.de>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Adrian Bunk <bunk@stusta.de>
Cc: Chris Zubrzycki <chris@middle--earth.org>
Cc: Patrick Caulfield <pcaulfie@redhat.com>