iio: fix doc for iio_gts_find_sel_by_int_time

The kerneldoc for iio_gts_find_sel_by_int_time() has an error.
Documentation states that function is searching a selector for a HW-gain
while it is searching a selector for an integration time.

Fix the documentation by saying the function is looking for a selector
for an integration time.

Fixes: 38416c28 ("iio: light: Add gain-time-scale helpers")
Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Link: https://lore.kernel.org/r/ZEIjI4YUzqPZk/9X@fedora


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>