Add support for MPS step-down converter mp9941. This driver exposes
telemetry and limit value readings and writtings.
Signed-off-by: Noah Wang <noahwang.wang@outlook.com>
Link: https://lore.kernel.org/r/SEYPR04MB648294005D55F70736B519F6FAC72@SEYPR04MB6482.apcprd04.prod.outlook.com
[groeck: Include bitfield.h (for FIELD_PREP) and bits.h (for GENMASK)]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>