Bluetooth: Use hci_conn_hash_lookup_le() when possible

Use the new hci_conn_hash_lookup_le() API to look up LE connections.
This way we're guaranteed exact matches that also take into account
the address type.

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