drm/nouveau/disp: add a method to fetch info needed by drm vblank timestamping

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

diff --cc drivers/gpu/drm/nouveau/core/engine/disp/nv04.c
Simple merge

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

diff --cc drivers/gpu/drm/nouveau/core/engine/disp/nv50.h
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/engine/disp/nv84.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/engine/disp/nv94.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/engine/disp/nva3.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/engine/disp/nvd0.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/engine/disp/nve0.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/engine/disp/nvf0.c
Simple merge

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