drm/xe: Log when a timed out TLB invalidation ack finally arrives

When a TLB invalidation fence times out we log the timeout, but if the
ack for that seqno later shows up there is no record of it, making it
impossible to tell from logs whether the ack was lost forever or merely
(very) late.

Track the most recent timed out seqno and log how late its ack arrives,
relative to both the original request and the moment the fence was
signaled with -ETIME.

On ARL with GuC 70.53.0 this shows the acks are never lost: they
consistently arrive ~2.3s after the request, tens of milliseconds after
the TDR has already signaled the fence:

  TLB invalidation fence timeout, seqno=10992 recv=10991
  TLB invalidation late ack: seqno=10992 recv=10992,
    request-to-ack=2314ms, timeout-to-ack=45ms

Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/8678
Signed-off-by: Tales A. Mendonça <talesam@gmail.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260922144634.55130-3-talesam@gmail.com

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