lis3: fix misc device unregistering and printk

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: Eric Piel <eric.piel@tremplin-utc.net>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>