Bluetooth: controller: Sync ISO Establishment fixes

- Introduce variable in lll_sync_iso for sync establishment timeout
- Introduce estab_failed flag in event_done_extra struct to convey
  establishment failure from LLL.
- Fix ull_sync_iso_estab_done always sending success
- Return correct HCI error depending on prepare state

Signed-off-by: Morten Priess <mtpr@oticon.com>