extcon: Fix error handling in extcon_dev_register

When devm_kcalloc() fails, we should execute device_unregister()
to unregister edev->dev from system.

Fixes: 046050f6e623e ("extcon: Update the prototype of extcon_register_notifier() with enum extcon")
Signed-off-by: Dinghao Liu <[e-mail]>
Signed-off-by: Chanwoo Choi <[e-mail]>

drivers/extcon/extcon.c

···
 				sizeof(*edev->nh), GFP_KERNEL);
 	if (!edev->nh) {
 		ret = -ENOMEM;
+		device_unregister(&edev->dev);
 		goto err_dev;
 	}