drm/i915: move a gtt flush to the correct place

No functional change, because gtt flushing is a no-op. Still, try
to keep the bookkeeping accurate. The if is still slightly wrong
for with execbuf2 even i915-class hw doesn't always need a fence
reg for gpu access. But that's for somewhen lateron.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NEric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/i915_gem.c

@@ -2552,12 +2552,12 @@ i915_gem_object_put_fence_reg(struct drm_gem_object *obj)
 		int ret;
 
 		i915_gem_object_flush_gpu_write_domain(obj);
-		i915_gem_object_flush_gtt_write_domain(obj);
 		ret = i915_gem_object_wait_rendering(obj);
 		if (ret != 0)
 			return ret;
 	}
 
+	i915_gem_object_flush_gtt_write_domain(obj);
 	i915_gem_clear_fence_reg (obj);
 
 	return 0;