counter: Use container_of instead of drvdata to track counter_device

The counter core uses drvdata to find a struct counter_device from a
struct device. However as the device is a member of struct counter_device,
the lookup can be done faster (and a bit type safe) using container_of.

There are no other users of drvdata, so the call to dev_set_drvdata can
go away, too.
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20211230150300.72196-2-u.kleine-koenig@pengutronix.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/counter/counter-core.c

@@ -26,7 +26,8 @@ static DEFINE_IDA(counter_ida);
 
 static void counter_device_release(struct device *dev)
 {
-	struct counter_device *const counter = dev_get_drvdata(dev);
+	struct counter_device *const counter =
+		container_of(dev, struct counter_device, dev);
 
 	counter_chrdev_remove(counter);
 	ida_free(&counter_ida, dev->id);
@@ -78,7 +79,6 @@ int counter_register(struct counter_device *const counter)
 		dev->of_node = counter->parent->of_node;
 	}
 	device_initialize(dev);
-	dev_set_drvdata(dev, counter);
 
 	err = counter_sysfs_add(counter);
 	if (err < 0)