hwmon: (pmbus/max16601) Add support for MAX16600

From programming perspective, MAX16600 is identical to MAX16601 and
MAX16602. Add support for it.

Cc: Steve Foreman <foremans@google.com>
Cc: Holly Barrett <holly.barrett@analog.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>