drm/i915: Simplify flushing activity on the ring

As we now always preallocate the seqno before writing to the ring, we
can trivially test if we have any pending activity on the ring by
inspecting the olr. This makes it then possible to flush operations that
are not normally associated with a request, like power-management.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem.c

@@ -2485,13 +2485,9 @@ static int i915_ring_idle(struct intel_ring_buffer *ring)
 	u32 seqno;
 	int ret;
 
-	/* We need to add any requests required to flush the objects */
-	if (!list_empty(&ring->active_list)) {
-		seqno = list_entry(ring->active_list.prev,
-				   struct drm_i915_gem_object,
-				   ring_list)->last_read_seqno;
-
-		ret = i915_gem_check_olr(ring, seqno);
+	/* We need to add any requests required to flush the objects and ring */
+	if (ring->outstanding_lazy_request) {
+		ret = i915_add_request(ring, NULL, NULL);
 		if (ret)
 			return ret;
 	}