Bluetooth: Host: df: Fix uninit per adv sync and IQ report passed to app

In case of error in hci_df_prepare_connectionless_iq_report function
e.g. due to wrong periodic advertising sync handle, uninitilized
per_adv_sync and IQ report object were passed by cte_report_cb callback
to an application.

Correct behavior in such situation is to not to cal cte_report_cb callback.

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