Bluetooth: fix an error code in hci_register_dev()

Preserve the error code from hci_register_suspend_notifier().  Don't
return success.

Fixes: d6bb2a91f95b ("Bluetooth: Unregister suspend with userchannel")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>