Another subset of the more recent batch of Chinese clones aren't specs-compliant and seem to lock up whenever they receive a HCI_OP_SET_EVENT_FLT with flt_type set to zero/HCI_FLT_CLEAR_ALL, which on Linux (until the recent HCI state-machine refactor) happened right at BR/EDR setup. As there are other less-straightforward ways of reaching those operations, this patch is still relevant. So, while all the previous efforts to wrangle the herd of fake CSRs seem to be paying off (and these also get detected as such) we still need to take care of this quirk; testers seem to agree that these dongles tend to work well enough afterwards.
