Fix possible race condition.
It is not allowed to return with an error code after RTC is registered.
Suggested-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: NDenis Osterland <Denis.Osterland@diehl.com>
Reviewed-by: NMichael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@bootlin.com>