drm/i915: Mark the removal of the i915_request from the sched.link

Keep the rq->fence.flags consistent with the status of the
rq->sched.link, and clear the associated bits when decoupling the link
on retirement (as we may wish to inspect those flags independent of
other state).

Fixes: 32ff621fd7 ("drm/i915/gt: Allow temporary suspension of inflight requests")
References: https://gitlab.freedesktop.org/drm/intel/issues/997
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200122140243.495621-3-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_request.c

@@ -221,6 +221,8 @@ static void remove_from_engine(struct i915_request *rq)
 		locked = engine;
 	}
 	list_del_init(&rq->sched.link);
+	clear_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
+	clear_bit(I915_FENCE_FLAG_HOLD, &rq->fence.flags);
 	spin_unlock_irq(&locked->active.lock);
 }