iio: light: tsl2591: delete a stray tab

This return statement is indented one more tab than it should be.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YJ523y0dhc1IwCOB@mwandaSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>