hwmon: (pmbus) Add ltc4286 driver

Add a driver to support ltc4286 chip

Signed-off-by: Delphine CC Chiu <Delphine_CC_Chiu@Wiwynn.com>
Link: https://lore.kernel.org/r/20231123015440.199822-3-Delphine_CC_Chiu@Wiwynn.com
[groeck: Fixed formatting]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>