drm/nouveau/fifo: split user classes out from engine implementations

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

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

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

drivers/gpu/drm/nouveau/nvkm/engine/fifo/chan.c

drivers/gpu/drm/nouveau/nvkm/engine/fifo/chan.h

drivers/gpu/drm/nouveau/nvkm/engine/fifo/chang84.c

drivers/gpu/drm/nouveau/nvkm/engine/fifo/changf100.h

drivers/gpu/drm/nouveau/nvkm/engine/fifo/changk104.h

drivers/gpu/drm/nouveau/nvkm/engine/fifo/channv04.h

drivers/gpu/drm/nouveau/nvkm/engine/fifo/channv50.c

drivers/gpu/drm/nouveau/nvkm/engine/fifo/channv50.h

drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmag84.c

drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv04.c

drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv10.c

drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv17.c

drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv40.c

drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv50.c

drivers/gpu/drm/nouveau/nvkm/engine/fifo/g84.c

drivers/gpu/drm/nouveau/nvkm/engine/fifo/gf100.c

drivers/gpu/drm/nouveau/nvkm/engine/fifo/gf100.h