soc: stm32h7: Fails to boot with LDO power supply, if soc has SMPS support.

[alexanderendian]

Describe the bug
In soc_m7.c, SMPS is enabled if the soc has SMPS-support, without regard for the actual board design. For boards designed to use LDO, enabling SMPS causes the microcontroller to reset, presumably due to losing power.

To Reproduce
Run Zephyr on a STM32H7 design with LDO supply using a part which supports SMPS.

Expected behavior
The choice between SMPS and LDO should be configurable on a per board basis.

Impact
No impact for the moment as it can be worked around by commenting out the SMPS path in soc_m7.c.

Related issues
#34732 - also regarding power config of STM32H7.

[erwango]

@ABOSTM Feel free to close if duplicate of #34732

[ABOSTM]

Duplicate of #34732