thermal: hwmon: Use extra_groups for adding temperature attributes

thermal: hwmon: Use extra_groups for adding temperature attributes

Instead of passing NULL as the last argument to __hwmon_device_register()
in hwmon_device_register_for_thermal() and then adding each temperature
sysfs attribute to the hwmon device via device_create_file(), redefine
hwmon_device_register_for_thermal() to take an extra_groups argument
that will be passed to __hwmon_device_register(), define an attribute
group with a proper .is_visible() callback for the temperature
attributes and a related attribute groups pointer, and pass the latter
to hwmon_device_register_for_thermal().

This causes the code to be way more straightforward and closer to
what the other users of the hwmon subsystem do.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/8704209.T7Z3S40VBb@rafael.j.wysocki
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>