regulator: mcp16502: Add supplier for regulators

regulator: mcp16502: Add supplier for regulators

Based on the datasheet [1] (Block Diagram) PVIN[1-4] and LVIN
represent the input voltage supply for each BUCKs respective LDOs.
Update the driver to align with the datasheet [1].

[1]: https://ww1.microchip.com/downloads/aemDocuments/documents/APID/ProductDocuments/DataSheets/MCP16502-Data-Sheet-DS20006275.pdf

Co-developed-by: Mihai Sain <mihai.sain@microchip.com>
Signed-off-by: Mihai Sain <mihai.sain@microchip.com>
Signed-off-by: Andrei Simion <andrei.simion@microchip.com>
Link: https://patch.msgid.link/20240812135231.43744-2-andrei.simion@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>