drm/nv50-nvaf/fb: split the class definitions up a bit

These will diverge further in the future.

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

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

diff --cc drivers/gpu/drm/nouveau/core/engine/device/nv50.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/include/subdev/fb.h
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/fb/nv50.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/fb/nv50.h
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/fb/nv84.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/fb/nva3.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/fb/nvaa.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/fb/nvaf.c
Simple merge