drm/nouveau/gpio: use indirect pointer to base class definition

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

diff --cc drivers/gpu/drm/nouveau/core/engine/device/gm100.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/engine/device/nv10.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/engine/device/nv20.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/engine/device/nv30.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/engine/device/nv40.c
Simple merge

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

diff --cc drivers/gpu/drm/nouveau/core/engine/device/nvc0.c
Simple merge

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

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

diff --cc drivers/gpu/drm/nouveau/core/subdev/gpio/nv10.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/gpio/nv50.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/gpio/nvd0.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/subdev/gpio/nve0.c
Simple merge