rtc: pm8xxx: fix possible race condition

probe must not fail after devm_rtc_register_device is successful because
the character device will be seen by userspace and may be opened right
away. Call it last to avoid opening the race window.

Link: https://lore.kernel.org/r/20250303223600.1135142-2-alexandre.belloni@bootlin.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>