iio: light: gp2ap002: Fix rumtime PM imbalance on error

iio: light: gp2ap002: Fix rumtime PM imbalance on error

When devm_request_threaded_irq() fails, we should decrease the
runtime PM counter to keep the counter balanced. But when
iio_device_register() fails, we need not to decrease it because
we have already decreased it before.

Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Fixes: 97d642e23037 ("iio: light: Add a driver for Sharp GP2AP002x00F")
Link: https://lore.kernel.org/r/20210407034927.16882-1-dinghao.liu@zju.edu.cn
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>