drivers: usb_c: rt1715: fix uncheck return value cid issue

fix `gpio_add_callback` unchecked return value issue

Signed-off-by: Jilay Pandya <jilay.pandya@outlook.com>

drivers/usb_c/tcpc/rt1715.c

diff --git a/drivers/usb_c/tcpc/rt1715.c b/drivers/usb_c/tcpc/rt1715.c
index fe34eea..a1941eb 100644
--- a/drivers/usb_c/tcpc/rt1715.c
+++ b/drivers/usb_c/tcpc/rt1715.c
@@ -618,7 +618,14 @@
 	gpio_pin_configure_dt(&cfg->alert_gpio, GPIO_INPUT);
 
 	gpio_init_callback(&data->alert_cb, rt1715_alert_cb, BIT(cfg->alert_gpio.pin));
-	gpio_add_callback(cfg->alert_gpio.port, &data->alert_cb);
+
+	ret = gpio_add_callback(cfg->alert_gpio.port, &data->alert_cb);
+
+	if (ret != 0) {
+		LOG_ERR("Failed to add alert callback: %d", ret);
+		return;
+	}
+
 	gpio_pin_interrupt_configure_dt(&cfg->alert_gpio, GPIO_INT_EDGE_TO_ACTIVE);
 
 	tcpci_init_alert_mask(data->dev);