drm/nouveau: implement a simple sysfs interface to new pm code

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

diff --cc drivers/gpu/drm/nouveau/Makefile
Simple merge

diff --cc drivers/gpu/drm/nouveau/nouveau_drm.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/nouveau_drm.h
Simple merge

diff --cc drivers/gpu/drm/nouveau/nouveau_sysfs.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/nouveau_sysfs.h
Simple merge