Fix failure exits in asus-laptop

Fallout from f8a7c6fe.  However, looking
at it shows that checks done in ASUS_LED_UNREGISTER() can't trigger
at all (we never get to asus_led_exit() if registration fails) and
if that registration fails, we actually leak stuff.  IOW, it's worse
than just replacing class_dev with dev in there - the tests themselves
had been papering over the lousy cleanup logics.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Michal Piotrowski <michal.k.k.piotrowski@gmail.com>
Cc: Corentin Chary <corentincj@iksaif.net>
Cc: Karol Kozimor <sziwan@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>