drm/nouveau/gr: convert user classes to new-style nvkm_object

drivers/gpu/drm/nouveau/include/nvif/device.h

drivers/gpu/drm/nouveau/include/nvkm/core/client.h

drivers/gpu/drm/nouveau/include/nvkm/engine/gr.h

drivers/gpu/drm/nouveau/nvkm/core/client.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/Kbuild

drivers/gpu/drm/nouveau/nvkm/engine/gr/base.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgf100.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgf100.h

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgf104.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgf108.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgf110.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgf117.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgf119.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgk104.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgk110.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgk110b.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgk208.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgk20a.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgm107.c

drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgm204.c