extcon: Fix build warning for extcon_unregister_notifier comment

Give the line the asterisk it wanted to fix the build warning.

[Build warning message]
Building with W=1 reports:

  CC      drivers/extcon/devres.o
drivers/extcon/devres.c:208: warning: bad line:
	- Resource-managed extcon_unregister_notifier()
Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
[cw00.choi: Edit the patch subject and description]
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

drivers/extcon/devres.c

@@ -205,7 +205,7 @@ EXPORT_SYMBOL(devm_extcon_register_notifier);
 
 /**
  * devm_extcon_unregister_notifier()
-			- Resource-managed extcon_unregister_notifier()
+ *			- Resource-managed extcon_unregister_notifier()
  * @dev:	the device owning the extcon device being created
  * @edev:	the extcon device
  * @id:		the unique id among the extcon enumeration