mfd: cros_ec: Check DT node for usbpd-notify add

Add a check to ensure there is indeed an EC device tree entry before
adding the cros-usbpd-notify device. This covers configs where both
CONFIG_ACPI and CONFIG_OF are defined, but the EC device is defined
using device tree and not in ACPI.

Fixes: 4602dce0 ("mfd: cros_ec: Add cros-usbpd-notify subdevice")
Signed-off-by: Prashant Malani <pmalani@chromium.org>
Tested-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/cros_ec_dev.c

@@ -211,7 +211,7 @@ static int ec_device_probe(struct platform_device *pdev)
 	 * explicitly added on platforms that don't have the PD notifier ACPI
 	 * device entry defined.
 	 */
-	if (IS_ENABLED(CONFIG_OF)) {
+	if (IS_ENABLED(CONFIG_OF) && ec->ec_dev->dev->of_node) {
 		if (cros_ec_check_features(ec, EC_FEATURE_USB_PD)) {
 			retval = mfd_add_hotplug_devices(ec->dev,
 					cros_usbpd_notify_cells,