drm/xe: Block reset while recovering from VF migration

Resetting GuC during recovery could interfere with the recovery
process. Such reset might be also triggered without justification,
due to migration taking time, rather than due to the workload not
progressing.

Doing GuC reset during the recovery would cause exit of RESFIX state,
and therefore continuation of GuC work while fixups are still being
applied. To avoid that, reset needs to be blocked during the recovery.

This patch blocks the reset during recovery. Reset request in that
time range will be stalled, and unblocked only after GuC goes out
of RESFIX state.

In case a reset procedure already started while the recovery is
triggered, there isn't much we can do - we cannot wait for it to
finish as it involves waiting for hardware, and we can't be sure
at which exact point of the reset procedure the GPU got switched.
Therefore, the rare cases where migration happens while reset is
in progress, are still dangerous. Resets are not a part of the
standard flow, and cause unfinished workloads - that will happen
during the reset interrupted by migration as well, so it doesn't
diverge that much from what normally happens during such resets.

v2: Introduce a new atomic for reset blocking, as we cannot reuse
  `stopped` atomic (that could lead to losing a workload).
v3: Switched atomic functs to ones which include proper barriers

Signed-off-by: Tomasz Lis <tomasz.lis@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Reviewed-by: Michal Winiarski <michal.winiarski@intel.com>
Link: https://lore.kernel.org/r/20250802031045.1127138-4-tomasz.lis@intel.com
Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>

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