Bluetooth: Add HCI status return parameter to hci_req_sync()

In some cases it may be important to get the exact HCI status rather
than the converted HCI-to-errno value. Add an optional return
parameter to the hci_req_sync() API to allow for this. Since there are
no good HCI translation candidates for cancelation and timeout, use
the "unknown" status code for those cases.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>