iio: inkern: call iio_device_put() only on mapped devices

In the error path of iio_channel_get_all(), iio_device_put() is called
on all IIO devices, which can cause a refcount imbalance. Fix this error
by calling iio_device_put() only on IIO devices whose refcounts were
previously incremented by iio_device_get().

Fixes: 314be14 ("iio: Rename _st_ functions to loose the bit that meant the staging version.")
Signed-off-by: Joe Hattori <joe@pf.is.s.u-tokyo.ac.jp>
Link: https://patch.msgid.link/20241204111342.1246706-1-joe@pf.is.s.u-tokyo.ac.jp
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/inkern.c

@@ -500,7 +500,7 @@ struct iio_channel *iio_channel_get_all(struct device *dev)
 	return_ptr(chans);
 
 error_free_chans:
-	for (i = 0; i < nummaps; i++)
+	for (i = 0; i < mapind; i++)
 		iio_device_put(chans[i].indio_dev);
 	return ERR_PTR(ret);
 }