Bluetooth: Clear pending connections from hci_conn_params_clear

When hci_conn_params_clear is called, it is always followed by a
call to hci_pend_le_conns_clear. So instead of making this explicit
just make sure it is always called. This makes this function similar
on how hci_conn_params_add and hci_conn_params_del work.

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