Fixes the F1.1 review finding. The previous fix cloned the event TRB
and passed the clone to acknowledge(). trb.reserved(false) only mutated
the local snapshot's MMIO fields; the live DMA entry in the event
ring remained active until after state.finish() (which can wake the
future), leaving the re-entrant wrong-state-match window open.
Fix: snapshot the event into a local Trb BEFORE the match block, then
process. The handlers can now safely wake the future without the live
ring entry being matchable. event_trb.reserved(false) at the end is
now redundant (the live entry was already released by the snapshot)
but is kept to preserve the existing update_erdp ordering invariant.
Red Bear OS
dd0127b635