rtc: sun6i: let the core handle rtc range

Let the rtc core check the date/time against the RTC range.

Tested-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Link: https://lore.kernel.org/r/20200330201226.860967-1-alexandre.belloni@bootlin.com


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