drm/nouveau/fb: implement various bits of work towards memory reclocking

drivers/gpu/drm/nouveau/Makefile

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

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

drivers/gpu/drm/nouveau/core/subdev/clock/pllnva3.c

drivers/gpu/drm/nouveau/core/subdev/fb/gddr5.c

drivers/gpu/drm/nouveau/core/subdev/fb/nv40.h

drivers/gpu/drm/nouveau/core/subdev/fb/nvc0.c

drivers/gpu/drm/nouveau/core/subdev/fb/nvc0.h

drivers/gpu/drm/nouveau/core/subdev/fb/nve0.c

drivers/gpu/drm/nouveau/core/subdev/fb/priv.h

drivers/gpu/drm/nouveau/core/subdev/fb/ramfuc.h

drivers/gpu/drm/nouveau/core/subdev/fb/ramnv40.c

drivers/gpu/drm/nouveau/core/subdev/fb/ramnv41.c

drivers/gpu/drm/nouveau/core/subdev/fb/ramnv44.c

drivers/gpu/drm/nouveau/core/subdev/fb/ramnv49.c

drivers/gpu/drm/nouveau/core/subdev/fb/ramnv50.c

drivers/gpu/drm/nouveau/core/subdev/fb/ramnva3.c

drivers/gpu/drm/nouveau/core/subdev/fb/ramnvc0.c

drivers/gpu/drm/nouveau/core/subdev/fb/ramnve0.c

drivers/gpu/drm/nouveau/core/subdev/fb/ramseq.h