Bluetooth: Fix debugfs entry leak in hci_register_dev()

Fault injection test report debugfs entry leak as follows:

debugfs: Directory 'hci0' with parent 'bluetooth' already present!

When register_pm_notifier() failed in hci_register_dev(), the debugfs
create by debugfs_create_dir() do not removed in the error handing path.

Add the remove debugfs code to fix it.

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>