Bluetooth: controller: Add release of chains when get latest adv pdu

Add release of chained PDUs by lll_adv_pdu_and_extra_data_-
latest_get function. It is requier to release unused
PDUs from a chain to avoid PDUs leakage.
It maight happen when chained PDUs were used by Direction
Finding, then lll_adv_pdu_and_extra_data_lates_get is used
instead of lll_adv_pdu_lates_get.

Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>