hwmon: (ds1621) Add ds1631 chip support to ds1621 driver and documentation

Add definitions, information, and code for ds1631 chip support
to the ds1621 driver.

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 0114ed4..4f71370 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -355,6 +355,7 @@
 	  Integrated DS1621 sensor chips and compatible models including:
 
 	  - Dallas Semiconductor DS1625
+	  - Maxim Integrated DS1631
 	  - Maxim Integrated DS1721
 
 	  This driver can also be built as a module.  If so, the module