If bt_init() fails, the debugfs directory currently is not removed. If
the module is loaded again after that, the debugfs directory is not set
up properly due to the existing directory.

  # modprobe bluetooth
  # ls -laF /sys/kernel/debug/bluetooth
  total 0
  drwxr-xr-x  2 root root 0 Sep 27 14:26 ./
  drwx------ 31 root root 0 Sep 27 14:25 ../
  -r--r--r--  1 root root 0 Sep 27 14:26 l2cap
  -r--r--r--  1 root root 0 Sep 27 14:26 sco
  # modprobe -r bluetooth
  # ls -laF /sys/kernel/debug/bluetooth
  ls: cannot access '/sys/kernel/debug/bluetooth': No such file or directory
  #

  # modprobe bluetooth
  modprobe: ERROR: could not insert 'bluetooth': Invalid argument
  # dmesg | tail -n 6
  Bluetooth: Core ver 2.22
  NET: Registered PF_BLUETOOTH protocol family
  Bluetooth: HCI device and connection manager initialized
  Bluetooth: HCI socket layer initialized
  Bluetooth: Faking l2cap_init() failure for testing
  NET: Unregistered PF_BLUETOOTH protocol family
  # ls -laF /sys/kernel/debug/bluetooth
  total 0
  drwxr-xr-x  2 root root 0 Sep 27 14:31 ./
  drwx------ 31 root root 0 Sep 27 14:26 ../
  #

  # modprobe bluetooth
  # dmesg | tail -n 7
  Bluetooth: Core ver 2.22
  debugfs: Directory 'bluetooth' with parent '/' already present!
  NET: Registered PF_BLUETOOTH protocol family
  Bluetooth: HCI device and connection manager initialized
  Bluetooth: HCI socket layer initialized
  Bluetooth: L2CAP socket layer initialized
  Bluetooth: SCO socket layer initialized
  # ls -laF /sys/kernel/debug/bluetooth
  total 0
  drwxr-xr-x  2 root root 0 Sep 27 14:31 ./
  drwx------ 31 root root 0 Sep 27 14:26 ../
  #

Cc: stable@vger.kernel.org
Fixes: ffcecac6 ("Bluetooth: Create root debugfs directory during module init")
Signed-off-by: Aaron Thompson <dev@aaront.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>