drm/sun4i: Return if frontend is not present

Added return statement in sun4i_layer_format_mod_supported()
in case frontend is not present.

Signed-off-by: Saud Farooqui <farooqui_saud@hotmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/PA4P189MB1421E93EF5F8E8E00E71B7878BB29@PA4P189MB1421.EURP189.PROD.OUTLOOK.COM

Author: fsaud

drivers/gpu/drm/sun4i/sun4i_layer.c

@@ -117,7 +117,7 @@ static bool sun4i_layer_format_mod_supported(struct drm_plane *plane,
 	struct sun4i_layer *layer = plane_to_sun4i_layer(plane);
 
 	if (IS_ERR_OR_NULL(layer->backend->frontend))
-		sun4i_backend_format_is_supported(format, modifier);
+		return sun4i_backend_format_is_supported(format, modifier);
 
 	return sun4i_backend_format_is_supported(format, modifier) ||
 	       sun4i_frontend_format_is_supported(format, modifier);