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: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>