Bluetooth: mgmt: Translate HCI reason in Device Disconnected event

Bluetooth: mgmt: Translate HCI reason in Device Disconnected event

MGMT_EV_DEVICE_DISCONNECTED carries a reason field which is defined to
be one of MGMT_DEV_DISCONN_* (0x00..0x05). hci_disconn_complete_evt()
converts the HCI error with hci_to_mgmt_reason(), but two other paths
pass the raw HCI error straight through:

  hci_cs_disconnect()   -> cp->reason
  mgmt_connect_failed() -> status

The latter is reached whenever the adapter is powered off or suspended:
hci_disconnect_all_sync() aborts every link with
HCI_ERROR_REMOTE_POWER_OFF, hci_disconnect_sync() deliberately does not
wait for HCI_EV_DISCONN_COMPLETE for that reason, so that
hci_abort_conn_sync() finishes the connection off through
hci_conn_failed() instead.

As a result userspace sees an out of range reason:

  @ MGMT Event: Device Disconnected (0x000c) plen 8
        BR/EDR Address: 8C:A9:6F:2C:51:46
        Reason: Reserved (0x15)

  bluetoothd: btd_bearer_disconnected() Unknown disconnection value: 21
  bluetoothd: device_disconnected() Unknown disconnection value: 21

Export hci_to_mgmt_reason() and use it in both places, so that a power
off is reported as MGMT_DEV_DISCONN_REMOTE rather than as the raw
HCI_ERROR_REMOTE_POWER_OFF (0x15).

Fixes: d47da6bd4cfa ("Bluetooth: hci_core: Fix sending MGMT_EV_CONNECT_FAILED")
Fixes: 182ee45da083 ("Bluetooth: hci_sync: Rework hci_suspend_notifier")
Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>