extcon: Fix some kernel-doc comments

Add the description of @id in extcon_sync() kernel-doc comment
and @edev, @id, @prop in extcon_set_property_sync() kernel-doc
comment to remove warnings found by running scripts/kernel-doc,
which is caused by using 'make W=1'.
drivers/extcon/extcon.c:409: warning: Function parameter or
member 'id' not described in 'extcon_sync'
drivers/extcon/extcon.c:750: warning: Function parameter or
member 'edev' not described in 'extcon_set_property_sync'
drivers/extcon/extcon.c:750: warning: Function parameter or
member 'id' not described in 'extcon_set_property_sync'
drivers/extcon/extcon.c:750: warning: Function parameter or
member 'prop' not described in 'extcon_set_property_sync'
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

drivers/extcon/extcon.c

@@ -399,6 +399,7 @@ static ssize_t cable_state_show(struct device *dev,
 /**
  * extcon_sync() - Synchronize the state for an external connector.
  * @edev:	the extcon device
+ * @id:		the unique id indicating an external connector
  *
  * Note that this function send a notification in order to synchronize
  * the state and property of an external connector.
@@ -736,6 +737,9 @@ EXPORT_SYMBOL_GPL(extcon_set_property);
 
 /**
  * extcon_set_property_sync() - Set property of an external connector with sync.
+ * @edev:	the extcon device
+ * @id:		the unique id indicating an external connector
+ * @prop:	the property id indicating an extcon property
  * @prop_val:	the pointer including the new value of extcon property
  *
  * Note that when setting the property value of external connector,