drm/nouveau: fix null ptr dereferences on some boards

Regression from "device: populate master subdev pointer only when fully
constructed"

Reported-by: Bob Gleitsmann <rjgleits@bellsouth.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

diff --cc drivers/gpu/drm/nouveau/core/include/subdev/i2c.h
Simple merge

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

diff --cc drivers/gpu/drm/nouveau/core/subdev/i2c/base.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/therm/ic.c
Simple merge

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

diff --cc drivers/gpu/drm/nouveau/dispnv04/tvnv04.c
Simple merge