drm/nve0/fifo: allow copy engine channel to be looked up by instance

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/core/engine/fifo/nve0.c b/drivers/gpu/drm/nouveau/core/engine/fifo/nve0.c
index bd67906..0271337 100644
--- a/drivers/gpu/drm/nouveau/core/engine/fifo/nve0.c
+++ b/drivers/gpu/drm/nouveau/core/engine/fifo/nve0.c
@@ -137,9 +137,11 @@
 
 	switch (nv_engidx(object->engine)) {
 	case NVDEV_ENGINE_SW   :
+		return 0;
 	case NVDEV_ENGINE_COPY0:
 	case NVDEV_ENGINE_COPY1:
 	case NVDEV_ENGINE_COPY2:
+		nv_engctx(ectx)->addr = nv_gpuobj(base)->addr >> 12;
 		return 0;
 	case NVDEV_ENGINE_GR   : addr = 0x0210; break;
 	case NVDEV_ENGINE_BSP  : addr = 0x0270; break;