drm/sun4i: Add end of list element for sun4i_layers_init's returned list

The number of defined planes in sun4i_layer is unknown to other parts
of the sun4i drm driver. Since the return value of sun4i_layers_init
is a list of layers, make it return 1 more empty layer as an end of
list guard value.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

drivers/gpu/drm/sun4i/sun4i_layer.c

@@ -139,7 +139,7 @@ struct sun4i_layer **sun4i_layers_init(struct drm_device *drm)
 	struct sun4i_layer **layers;
 	int i;
 
-	layers = devm_kcalloc(drm->dev, ARRAY_SIZE(sun4i_backend_planes),
+	layers = devm_kcalloc(drm->dev, ARRAY_SIZE(sun4i_backend_planes) + 1,
 			      sizeof(*layers), GFP_KERNEL);
 	if (!layers)
 		return ERR_PTR(-ENOMEM);