hwmon: (adt7x10) Add alarm interrupt support

This allows an userspace application to poll() on the alarm files to get
notified in case of a temperature threshold event.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Reviewed-by: Hartmut Knaack <knaack.h@gmx.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>