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.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>