iio: light: opt3001: Fixed timeout error when 0 lux

Reading from sensor returned timeout error under
zero light conditions.

Signed-off-by: Jiri Valek - 2N <valek@2n.cz>
Fixes: ac663db3

 ("iio: light: opt3001: enable operation w/o IRQ")
Link: https://lore.kernel.org/r/20210920125351.6569-1-valek@2n.cz
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>