drm/nouveau/fence: use NVIDIA's headers for read()

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>

drivers/gpu/drm/nouveau/nv10_fence.c

@@ -52,7 +52,7 @@ nv10_fence_sync(struct nouveau_fence *fence,
 u32
 nv10_fence_read(struct nouveau_channel *chan)
 {
-	return nvif_rd32(&chan->user, 0x0048);
+	return NVIF_RD32(&chan->user, NV06E, REFERENCE);
 }
 
 void