Bluetooth: Fix handling of getpeername() for HCI sockets

The HCI sockets do not have a peer associated with it and so make sure
that getpeername() returns EOPNOTSUPP since this operation is actually
not supported on HCI sockets.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>