regulator: Add Renesas PMIC RAA215300 driver

regulator: Add Renesas PMIC RAA215300 driver

The RAA215300 is a 9-channel PMIC that consists of
 * Internally compensated regulators
 * built-in Real Time Clock (RTC)
 * 32kHz crystal oscillator
 * coin cell battery charger

The RTC on RAA215300 is similar to the IP found in the ISL1208.
The existing driver for the ISL1208 works for this PMIC too,
however the RAA215300 exposes two devices via I2C, one for the RTC
IP, and one for everything else. The RTC IP has to be enabled
by the other I2C device, therefore this driver is necessary to get
the RTC to work.

The external oscillator bit is inverted on PMIC version 0x11.

Add PMIC RAA215300 driver for enabling RTC block and instantiating
RTC device based on PMIC version.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/Message-Id:
Signed-off-by: Mark Brown <broonie@kernel.org>