drm/syncobj: add missing error return code in drm_syncobj_transfer_to_timeline()

If dma_fence_unwrap_merge() fails, it should return error code
in drm_syncobj_transfer_to_timeline()

Fixes: ec8d985f ("drm: use dma_fence_unwrap_merge() in drm_syncobj")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220613063454.2609364-1-yangyingliang@huawei.com

drivers/gpu/drm/drm_syncobj.c

@@ -874,8 +874,10 @@ static int drm_syncobj_transfer_to_timeline(struct drm_file *file_private,
 
 	fence = dma_fence_unwrap_merge(tmp);
 	dma_fence_put(tmp);
-	if (!fence)
+	if (!fence) {
+		ret = -ENOMEM;
 		goto err_put_timeline;
+	}
 
 	chain = dma_fence_chain_alloc();
 	if (!chain) {