nimble/ll: Make sure aux_data is valid when sending ext adv report
nimble/ll: Make sure aux_data is valid when sending ext adv report

In ble_ll_hci_send_ext_adv_report() we have to have valid aux_data.
Assert if it is not a case.

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble