Bluetooth: Use hci_conn_params in pend_le_conns

Since the connection parameters are always a basis for adding entries to
hdev->pend_le_conns (so far of type bdaddr_list) it's simpler and more
efficient to have the parameters themselves be the entries in the
pend_le_conns list. We do this by adding another list_head to the
hci_conn_params struct.

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