powercap: call put_device() on an error path in powercap_register_control_type()

powercap_register_control_type() calls device_register(), but does not
release the refcount of the device when it fails.

Call put_device() before returning an error to balance the refcount.

Since the kfree(control_type) will be done by powercap_release(), remove
the lines in powercap_register_control_type() before returning the error.

This bug was found by an experimental verifier that I am developing.

Signed-off-by: Joe Hattori <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
[ rjw: Changelog edits ]
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/powercap/powercap_sys.c

···
 	dev_set_name(&control_type->dev, "%s", name);
 	result = device_register(&control_type->dev);
 	if (result) {
-		if (control_type->allocated)
-			kfree(control_type);
+		put_device(&control_type->dev);
 		return ERR_PTR(result);
 	}
 	idr_init(&control_type->idr);