Bluetooth: Remove unneeded locking

We don't need locking hdev in hci_conn_timeout() since it doesn't
access any hdev's shared resources, it basically queues HCI commands.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@openbossa.org>
Reviewed-by: Ulisses Furquim <ulisses@profusion.mobi>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>