drm/i915/gt: Ignore repeated attempts to suspend request flow across reset

Before reseting the engine, we suspend the execution of the guilty
request, so that we can continue execution with a new context while we
slowly compress the captured error state for the guilty context. However,
if the reset fails, we will promptly attempt to reset the same request
again, and discover the ongoing capture. Ignore the second attempt to
suspend and capture the same request.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/1168
Fixes: 32ff621f

 ("drm/i915/gt: Allow temporary suspension of inflight requests")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: <stable@vger.kernel.org> # v5.7+
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201204151234.19729-1-chris@chris-wilson.co.uk