power: supply: core: Add missing documentation for CHARGE_CONTROL_* properties

The existing POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT and
POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT_MAX properties
don't have documentation. I add that documentation here.

v5 changes:
- Split this commit out from the previous two commits.
Signed-off-by: Nick Crews <ncrews@chromium.org>
Reviewed-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Documentation/ABI/testing/sysfs-class-power

@@ -114,6 +114,25 @@ Description:
 		Access: Read
 		Valid values: Represented in microamps
 
+What:		/sys/class/power_supply/<supply_name>/charge_control_limit
+Date:		Oct 2012
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Maximum allowable charging current. Used for charge rate
+		throttling for thermal cooling or improving battery health.
+
+		Access: Read, Write
+		Valid values: Represented in microamps
+
+What:		/sys/class/power_supply/<supply_name>/charge_control_limit_max
+Date:		Oct 2012
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Maximum legal value for the charge_control_limit property.
+
+		Access: Read
+		Valid values: Represented in microamps
+
 What:		/sys/class/power_supply/<supply_name>/charge_control_start_threshold
 Date:		April 2019
 Contact:	linux-pm@vger.kernel.org