Enable 3.3 V and 5 V Regulators for Expansion Header on i.MX9 boards

[#1]

This patch series enables the external 3.3 V and 5 V power rails used by the Raspberry Pi expansion connector on the i.MX93-QSB, i.MX93-FRDM, and i.MX91-FRDM boards.

These regulators were already defined in the device tree but left disabled by default. By activating them, the RPI-compatible expansion header can properly power external modules, HATs, and add‑on boards.

Changes by board:

i.MX93-QSB

Enables the 3.3 V and 5 V external supply lines used by the RPI connector.

i.MX93-FRDM

Enables the 3.3 V and 5 V external supply lines used by the RPI connector.

i.MX91-FRDM

Enables the 3.3 V and 5 V external supply lines used by the RPI connector.

Purpose:

Provide proper power to the Raspberry Pi compatible expansion port.
Improve hardware compatibility for users attaching external HATs or modules.
Align all i.MX9 reference boards to use a consistent power‑tree configuration for the RPI connector.