The proper fix would have been to select LEDS_CLASS but this can lead
to a circular dependency, as found out by Arnd.

This patch implements Arnd's suggestion instead, at the cost of some
auto-magic for a fringe feature.
Reported-by: NArnd Bergmann <arnd@arndb.de>
Reported-by: Intel's 0-DAY
Fixes: 8d021d71 ("drm/nouveau/drm/nouveau: add a LED driver for the NVIDIA logo")
Signed-off-by: NMartin Peres <martin.peres@free.fr>
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>