hwmon_device_register() is a deprecated function and produces a warning.

Converting the driver to use the hwmon_device_register_with_groups()
instead.
Signed-off-by: Grant McEwan <grant.mcewan@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20190721225530.28799-2-grant.mcewan@alliedtelesis.co.nzSigned-off-by: Guenter Roeck <linux@roeck-us.net>