arm: mach-k3: am625_init: Add Erratum WA for RTC startup

In the first silicon revision of the am62x family of SoCs, the hardware
wakeup event cannot be used if software is unable to unlock the RTC
device within one second after boot. To work around this limitation
unlock RTC as soon as possible in the boot flow to maximize our chance
of linux being able to use this device.

Add the erratum i2327 workaround to initialize the RTC.

Signed-off-by: Nishanth Menon <nm@ti.com>
[bb@ti.com: rebased from 2021.01 and expanded commit and code messages]
Signed-off-by: Bryan Brattlof <bb@ti.com>