hwmon: (g762) Convert to hwmon_device_register_with_groups

Use ATTRIBUTE_GROUPS macro and hwmon_device_register_with_groups() to simplify
the code a bit.

Use hwmon_device_register_with_groups rather than the device managed version to
ensure g762_of_clock_disable() is called after hwmon_device_unregister().

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>