counter: ftm-quaddec: Convert to new counter registration

This fixes device lifetime issues where it was possible to free a live
struct device.

Fixes: a3b9a999 ("counter: add FlexTimer Module Quadrature decoder counter driver")
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/20211230150300.72196-19-u.kleine-koenig@pengutronix.de


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