hwmon: (emc1403) Add EMC1423 support

EMC1423 uses the similar register and adds a hardware shutdown pin to
protect exceed temperature. This function is set by resistor; it's not
necessary to do anything in the driver except add the emc1423 pid of 0x23.

Signed-off-by: Jekyll Lai <jekyll_lai@wistron.com>
[Updated Kconfig/comments and minor further changes asked for by the hwmon
 maintainers]
Signed-off-by: Alan Cox <alan@linux.intel.com>
[Fixed checkpatch warning]
Signed-of--by: Jean Delvare <khali@linux-fr.org>