rtc: isl1208: Add support for the built-in RTC on the PMIC RAA215300

The built-in RTC found on PMIC RAA215300 is the same as ISL1208.
However, the external oscillator bit is inverted on PMIC version
0x11. The PMIC driver detects PMIC version and instantiates the
RTC device based on i2c_device_id.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20230623140948.384762-11-biju.das.jz@bp.renesas.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>