drm/i915/execlists: Cache the last priolist lookup

static void unwind_incomplete_requests(struct intel_engine_cs *engine)

{

	struct drm_i915_gem_request *rq, *rn;

	struct i915_priolist *uninitialized_var(p);

	int last_prio = I915_PRIORITY_INVALID;

	lockdep_assert_held(&engine->timeline->lock);

	list_for_each_entry_safe_reverse(rq, rn,

					 &engine->timeline->requests,

					 link) {

		struct i915_priolist *p;

		if (i915_gem_request_completed(rq))

			return;

		__i915_gem_request_unsubmit(rq);

		unwind_wa_tail(rq);

		GEM_BUG_ON(rq->priotree.priority == I915_PRIORITY_INVALID);

		if (rq->priotree.priority != last_prio) {

			p = lookup_priolist(engine,

					    &rq->priotree,

					    rq->priotree.priority);

		list_add(&rq->priotree.link,

			 &ptr_mask_bits(p, 1)->requests);

			p = ptr_mask_bits(p, 1);

			last_prio = rq->priotree.priority;

		}

		list_add(&rq->priotree.link, &p->requests);

	}

}