Add Renesas PMIC RAA215300 and built-in RTC

Merge series from Biju Das <biju.das.jz@bp.renesas.com>:

This patch series aims to add support for Renesas PMIC RAA215300 and
built-in RTC found on this PMIC device.

The details of PMIC can be found here[1].

Renesas PMIC RAA215300 exposes two separate i2c devices, one for the main
device and another for rtc device.