Change from 3V3 to 1V8

[Ihysol]

Check all required changes to move from 3V3 to 1V8.

Use BUCK 4, since it can supply the greatest amount of current (2A).

[Ihysol]

1V8_rework branch added.

TODO: check if all previous connections still run with 1v8.

This was changed for STUSB VSYS, which requires 3V-5V.

Naming convention on STPMIC changed to BUCK#_ for clearance (BUCK3 and BUCK4 had collisions with the previous naming convention "BUCK_1V8").

[Ihysol]

List of connections to check for 1V8 compability:

• SD card - ?
• I2C (STUSB, Li-Ion) - OK
• eMMC - ?
• MP1 - ?