arm64: dts: imx8mp-kontron: Fix boot order for PMIC and RTC

arm64: dts: imx8mp-kontron: Fix boot order for PMIC and RTC

The PMIC provides a level-shifter for the I2C lines to the RTC. As the
level shifter needs to be enabled before the RTC can be accessed, make sure
that the PMIC driver is probed first.

As the PMIC also provides the supply voltage for the RTC through the 3.3V
regulator, simply express this in the DT to create the required dependency.

Avoid sporadic boot hangs that occurred when the RTC was accessed before
the level-shifter was enabled.

Fixes: 946ab10e3f40f ("arm64: dts: Add support for Kontron OSM-S i.MX8MP SoM and BL carrier board")
Signed-off-by: Annette Kobou <annette.kobou@kontron.de>
Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Frank Li <Frank.Li@nxp.com>