hwmon: Add driver for SMSC EMC2103 temperature monitor and fan controller

SMSC's EMC2103 family of temperature/fan controllers have 1
onboard and up to 3 external temperature sensors, and allow
closed-loop control of one fan.  This patch adds support for
them.

Signed-off-by: Steve Glendinning <steve.glendinning@smsc.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>