hwmon: (f71882fg) Cleanup sysfs attr creation 1/2

This patch makes a number of cleanups to the sysfs attr creation
in the f71882fg driver, this is a preparation patch for adding f71889fg
support:

* Add some comments to explain why some models need separate sysfs attr
  arrays for in / temp / fan / pwm
* Rename a number of sysfs attr arrays to make their function clearer
* Move the pwm#_auto_channels_temp attribute from the common to all
  models fan attr array to the per model auto mode pwm attr arrays, so
  that all the auto mode pwm attr are grouped together, and thus can be
  left out on models where we don't support auto pwm mode
* Put fan_beep attr in their own array, so that only auto mode pwm attr
  remain in the per model pwm sysfs attr arrays.
* Put the 4th special fan input for the f8000 in its own array, so that only
  auto mode pwm attr remain in the per model pwm sysfs attr arrays.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>