drm/nouveau/fifo: implement nvif event source

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

diff --cc drivers/gpu/drm/nouveau/core/engine/fifo/base.c
Simple merge

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

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

diff --cc drivers/gpu/drm/nouveau/core/engine/fifo/nv17.c
Simple merge

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

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

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

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

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

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

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

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

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