iio: light: iqs621: remove usage of iio_priv_to_dev()

We may want to get rid of the iio_priv_to_dev() helper. That's a bit
uncertain at this point. The reason is that we will hide some of the
members of the iio_dev structure (to prevent drivers from accessing them
directly), and that will also mean hiding the implementation of the
iio_priv_to_dev() helper inside the IIO core.

Hiding the implementation of iio_priv_to_dev() implies that some fast-paths
may not be fast anymore, so a general idea is to try to get rid of the
iio_priv_to_dev() altogether.

For this driver, removing iio_priv_to_dev() means keeping a reference
on the state struct.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Acked-by: Jeff LaBundy <jeff@labundy.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/iqs621-als.c

@@ -36,6 +36,7 @@
 
 struct iqs621_als_private {
 	struct iqs62x_core *iqs62x;
+	struct iio_dev *indio_dev;
 	struct notifier_block notifier;
 	struct mutex lock;
 	bool light_en;
@@ -103,7 +104,7 @@ static int iqs621_als_notifier(struct notifier_block *notifier,
 
 	iqs621_als = container_of(notifier, struct iqs621_als_private,
 				  notifier);
-	indio_dev = iio_priv_to_dev(iqs621_als);
+	indio_dev = iqs621_als->indio_dev;
 	timestamp = iio_get_time_ns(indio_dev);
 
 	mutex_lock(&iqs621_als->lock);
@@ -191,7 +192,7 @@ static int iqs621_als_notifier(struct notifier_block *notifier,
 static void iqs621_als_notifier_unregister(void *context)
 {
 	struct iqs621_als_private *iqs621_als = context;
-	struct iio_dev *indio_dev = iio_priv_to_dev(iqs621_als);
+	struct iio_dev *indio_dev = iqs621_als->indio_dev;
 	int ret;
 
 	ret = blocking_notifier_chain_unregister(&iqs621_als->iqs62x->nh,
@@ -551,6 +552,7 @@ static int iqs621_als_probe(struct platform_device *pdev)
 
 	iqs621_als = iio_priv(indio_dev);
 	iqs621_als->iqs62x = iqs62x;
+	iqs621_als->indio_dev = indio_dev;
 
 	if (iqs62x->dev_desc->prod_num == IQS622_PROD_NUM) {
 		ret = regmap_read(iqs62x->regmap, IQS622_IR_THRESH_TOUCH,