drm/nouveau: add support for gm204

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

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

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

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