charger-manager: of_cm_parse_desc() should be static

Fixes the following warning:

drivers/power/charger-manager.c:1539:21: warning: symbol
'of_cm_parse_desc' was not declared. Should it be static?
Signed-off-by: Anton Vorontsov <anton@enomsg.org>

drivers/power/charger-manager.c

@@ -1536,7 +1536,7 @@ static struct of_device_id charger_manager_match[] = {
 	{},
 };
 
-struct charger_desc *of_cm_parse_desc(struct device *dev)
+static struct charger_desc *of_cm_parse_desc(struct device *dev)
 {
 	struct charger_desc *desc;
 	struct device_node *np = dev->of_node;