hwmon: (pmbus/isl68137) Fix up chip IDs

I2C chip IDs need to reflect chip names, not chip functionality.

Fixes: f621d61f ("hwmon: (pmbus) add support for 2nd Gen Renesas digital multiphase")
Cc: Grant Peltier <grantpeltier93@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>