compal-laptop: Add charge control limit

Add charge control limit to the power supply subsystem of the Compal
platform driver.

This apparently was present in the original driver by Cezary Jackiewicz
at http://eko.one.pl/index.php?page=compal-laptop but it seems to have been
overlooked.

The Kconfig description is updated to reflect this addition. It now also
mentions the hwmon interface that was already present.

Signed-off-by: Roald Frederickx <roald.frederickx@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>

drivers/platform/x86/Kconfig

@@ -309,8 +309,8 @@ config COMPAL_LAPTOP
 	  This is a driver for laptops built by Compal, and some models by
 	  other brands (e.g. Dell, Toshiba).
 
-	  It adds support for rfkill, Bluetooth, WLAN and LCD brightness
-	  control.
+	  It adds support for rfkill, Bluetooth, WLAN, LCD brightness, hwmon
+	  and battery charging level control.
 
 	  For a (possibly incomplete) list of supported laptops, please refer
 	  to: Documentation/platform/x86-laptop-drivers.txt