iio: light: apds9306: Fix error handing

iio: light: apds9306: Fix error handing

The return value of 'iio_gts_find_int_time_by_sel()' is assigned to
variable 'intg_old' but value of 'ret' is checked for error. Update to
use 'intg_old' for error checking.

Fixes: 620d1e6c7a3f ("iio: light: Add support for APDS9306 Light Sensor")
Signed-off-by: Mudit Sharma <muditsharma.info@gmail.com>
Reviewed-by: Subhajit Ghosh <subhajit.ghosh@tweaklogic.com>
Link: https://patch.msgid.link/20240625210203.522179-1-muditsharma.info@gmail.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>