drm/nouveau: create base display from common code

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

diff --cc drivers/gpu/drm/nouveau/dispnv04/disp.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/dispnv04/disp.h
Simple merge

diff --cc drivers/gpu/drm/nouveau/nouveau_display.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/nouveau_display.h
Simple merge

diff --cc drivers/gpu/drm/nouveau/nouveau_drm.h
Simple merge

diff --cc drivers/gpu/drm/nouveau/nv50_display.c
Simple merge