drm/i915: Set fence_work.ops before dma_fence_init

Since dma_fence_init may call ops (because of a meaningless
trace_dma_fence), we need to set the worker ops prior to that call.
Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Fixes: 8e458fe2 ("drm/i915: Generalise the clflush dma-worker")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191212154224.1631531-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_sw_fence_work.c

@@ -78,12 +78,11 @@ static const struct dma_fence_ops fence_ops = {
 void dma_fence_work_init(struct dma_fence_work *f,
 			 const struct dma_fence_work_ops *ops)
 {
+	f->ops = ops;
 	spin_lock_init(&f->lock);
 	dma_fence_init(&f->dma, &fence_ops, &f->lock, 0, 0);
 	i915_sw_fence_init(&f->chain, fence_notify);
 	INIT_WORK(&f->work, fence_work);
-
-	f->ops = ops;
 }
 
 int dma_fence_work_chain(struct dma_fence_work *f, struct dma_fence *signal)