ARM: st: add new compatible for PWR regulators on

Merge series from Patrick Delaunay <patrick.delaunay@foss.st.com>:

This patchset adds the new PWR regulators compatible for STM32MP13:
"st,stm32mp13-pwr-reg".

As this node is just introduced by [1] and it is is not used by any
board in Linux,  it is the good time to introduced this compatible
and update the STM32MP13 SoC dtsi without ABI break.

A new compatible is needed as the content of the PWR_CR3 register,
used by this driver change with new bits on STM32MP13 for SD IO domain:
- bit 23: VDDSD2VALID
- bit 22: VDDSD1VALID
- bit 16: VDDSD2RDY
- bit 15: VDDSD2EN
- bit 14: VDDSD1RDY
- bit 13: VDDSD1EN

I will push a update on STM32MP13 SoC dtsi if this new compatible
is accepted to preserve the bisectability.

[1] commit f798f7079233 ("ARM: dts: stm32: add PWR regulators support on stm32mp131")
    https://lore.kernel.org/linux-arm-kernel/b89d0531-067f-4356-91b0-ed7434cee3d7@foss.st.com/