drm/tilcdc: Defer probe if there are no connectors

During probe there may not be any connectors yet if e.g. the panel
failed or hasn't been probed yet. I hitting this in practice the panels
probing was being delayed due to using a gpio backlight.

Fix this by returning -EPROBE_DEFER so the probing will be retried.
Signed-off-by: NSjoerd Simons <sjoerd.simons@collabora.co.uk>
Signed-off-by: NJyri Sarha <jsarha@ti.com>

drivers/gpu/drm/tilcdc/tilcdc_drv.c

@@ -378,7 +378,7 @@ static int tilcdc_init(struct drm_driver *ddrv, struct device *dev)
 	if (!priv->external_connector &&
 	    ((priv->num_encoders == 0) || (priv->num_connectors == 0))) {
 		dev_err(dev, "no encoders/connectors found\n");
-		ret = -ENXIO;
+		ret = -EPROBE_DEFER;
 		goto init_failed;
 	}