[PATCH] hwmon: Sysfs interface documentation update, 2 of 2, take 2

Reword and complete certain parts of the hwmon sysfs-interface
documentation file. Hopefully this will make things clearer for new
driver authors.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>