hwmon: (w83627ehf) Driver cleanup

- Moved fan pwm register array pointers into per-instance data.
- Only read fan pwm data for installed/supported fans.
- Update fan max output and fan step output information from data in
  registers.
- Create max_output and step_output attribute files only if respective
  fan pwm registers exist.

Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>