gpiolib: Fix error return code in gpiolib_dev_init()

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: 4731210c ("gpiolib: Bind gpio_device to a driver to enable fw_devlink=on by default")
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NBartosz Golaszewski <bgolaszewski@baylibre.com>

drivers/gpio/gpiolib.c

@@ -4256,7 +4256,8 @@ static int __init gpiolib_dev_init(void)
 		return ret;
 	}
 
-	if (driver_register(&gpio_stub_drv) < 0) {
+	ret = driver_register(&gpio_stub_drv);
+	if (ret < 0) {
 		pr_err("gpiolib: could not register GPIO stub driver\n");
 		bus_unregister(&gpio_bus_type);
 		return ret;