drm/nouveau: remove pointless assignment

self-assignment of a variable doesn't make a lot of sense.
Signed-off-by: Dave Jones <davej@fedoraproject.org>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_bo.c

@@ -982,7 +982,7 @@ nouveau_bo_move_m2mf(struct ttm_buffer_object *bo, int evict, bool intr,
 		     bool no_wait_gpu, struct ttm_mem_reg *new_mem)
 {
 	struct nouveau_drm *drm = nouveau_bdev(bo->bdev);
-	struct nouveau_channel *chan = chan = drm->ttm.chan;
+	struct nouveau_channel *chan = drm->ttm.chan;
 	struct nouveau_bo *nvbo = nouveau_bo(bo);
 	struct ttm_mem_reg *old_mem = &bo->mem;
 	int ret;