hwmon: (max6639) Add regulator support

Add regulator support for boards where the fan-supply have to be
powered up before it can be used.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Marcello Sylvester Bauer <sylv@sylv.io>
Link: https://lore.kernel.org/r/2cb9ed600fb43cdc604799746fbde2e2942cdca6.1643299570.git.sylv@sylv.io


Signed-off-by: Guenter Roeck <linux@roeck-us.net>