drm/nouveau/devinit: tidy up the subdev class definition

drivers/gpu/drm/nouveau/core/engine/device/nv04.c

drivers/gpu/drm/nouveau/core/engine/device/nv10.c

drivers/gpu/drm/nouveau/core/engine/device/nv20.c

drivers/gpu/drm/nouveau/core/engine/device/nv30.c

drivers/gpu/drm/nouveau/core/engine/device/nv40.c

drivers/gpu/drm/nouveau/core/engine/device/nv50.c

drivers/gpu/drm/nouveau/core/engine/device/nvc0.c

drivers/gpu/drm/nouveau/core/engine/device/nve0.c

drivers/gpu/drm/nouveau/core/include/subdev/devinit.h

drivers/gpu/drm/nouveau/core/subdev/clock/nv04.c

drivers/gpu/drm/nouveau/core/subdev/devinit/base.c

drivers/gpu/drm/nouveau/core/subdev/devinit/nv04.c

drivers/gpu/drm/nouveau/core/subdev/devinit/nv04.h

drivers/gpu/drm/nouveau/core/subdev/devinit/nv05.c

drivers/gpu/drm/nouveau/core/subdev/devinit/nv10.c

drivers/gpu/drm/nouveau/core/subdev/devinit/nv1a.c

drivers/gpu/drm/nouveau/core/subdev/devinit/nv20.c

drivers/gpu/drm/nouveau/core/subdev/devinit/nv50.c

drivers/gpu/drm/nouveau/core/subdev/devinit/nv50.h

drivers/gpu/drm/nouveau/core/subdev/devinit/nva3.c