hwmon: (ds1621) Add DS1731 chip support to ds1621 driver

These changes add DS1731 chip support to the ds1621 driver,
Kconfig, and documentation.

Signed-off-by: Robert Coulson <rob.coulson@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 4f71370..683c769 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -357,6 +357,7 @@
 	  - Dallas Semiconductor DS1625
 	  - Maxim Integrated DS1631
 	  - Maxim Integrated DS1721
+	  - Maxim Integrated DS1731
 
 	  This driver can also be built as a module.  If so, the module
 	  will be called ds1621.