hwmon: (pmbus) Add Infineon IRPS5401 driver

Add a driver to support the Infineon IRPS5401 PMIC. This chip has 5
pages corresponding to 4 switching outputs and one linear (LDO) output.
The switching and LDO outputs have slightly different supported
parameters.

Signed-off-by: Robert Hancock <hancock@sedsystems.ca>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>