Bluetooth: Controller: ISO BIS payload counter rollover

[carlst]

Describe the bug
The ISO bisPayloadCounter (value of tx->payload_count as set in subsys/bluetooth/controller/hci/hci.c, hci_iso_handle()) can rollover (e.g. after transmitting ISO data for ~10-11 minutes at 10ms rate, or 64K packets).

In subsys/bluetooth/controller/ll_sw/lll_adv.h, struct lll_adv_iso_stream
changing the line:
uint16_t pkt_seq_num
to:
uint64_t pkt_seq_num:39
seems to resolve the issue.

To Reproduce

1. Use nRF52840DK
2. Remove k_sleep(K_SECONDS(1)) in samples/bluetooth/iso_broadcast and log the various payload_count values near the memq_dequeue() calls in subsys/bluetooth/controller/ll_sw/nordic/lll/lll_adv_iso.c
3. AFter 64K packets and tx->payload_count rollover, 2 packets with same bisPayloadCounter occur.

Impact
Low priority

[carlescufi]

@carlst thanks for reporting! Why don’t you open a Pull Request with the suggested fix?

[carlst]

@carlescufi OK. Done. #44245