Can only unregister the misc device if it was registered before.  Also
remove debugging messages, which in addition were not properly formated.
Signed-off-by: NEric Piel <eric.piel@tremplin-utc.net>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>