RTC: Add QPNP rtc driver

A 32 bit RTC is housed inside PMIC. The RTC driver
uses SPMI interface to communicate with the RTC module.

RTC device is divided into two sub-peripherals:
1. RTC read-write peripheral having basic RTC registers.
2. Alarm peripheral for controlling alarm.

RTC peripherals are children of SPMI device and driver
receives it's configuration parameters (such as alarm
powerup feature to powerup phone using alarm interrupt)
from device tree.

Change-Id: I46a2ffc0f6c9c5ee174cf803de19e656da7ce088
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>