drm/nouveau/dp: probe dpcd to determine connectedness

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

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

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

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