drm/nv50/gr: move to exec engine interfaces

This needs a massive cleanup, but to catch bugs from the interface changes
vs the engine code cleanup, this will be done later.

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

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

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

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

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

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

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

diff --cc drivers/gpu/drm/nouveau/nv50_graph.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/nv50_vm.c
Simple merge