This patch introduces the driver for the RTC in the Allwinner A31 and
A23 SoCs.
Unlike the RTC found in A10/A20 SoCs, which was part of the timer, the
RTC in A31/A23 are a separate hardware block, which also contain a few
controls for the RTC block hardware (a regulator and RTC block GPIO pin
latches), while also having separate interrupts for the alarms.
The hardware is different enough to make a different driver for it.