hwmon: Add fan speed control features to w83627ehf

This patch adds long-awaited support for automatic fan modes. Based on
the work of Yuan Mu from Winbond, I finished the support with the great
help of David Hubbard.
Signed-off-by: Yuan Mu <Ymu@Winbond.com.tw>
Signed-off-by: Rudolf Marek <r.marek@sh.cvut.cz>
Signed-off-by: David Hubbard <david.c.hubbard@gmail.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>