drm/i915/gem: Reinitialise the local list before repeating

As we may start the loop again, we require our local list of i915_vma
we've processed to be reinitialised.

Fixes: aa5e445 ("drm/i915/gem: Try to flush pending unbind events")
Closes: https://gitlab.freedesktop.org/drm/intel/issues/731
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191205132912.606868-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -175,7 +175,7 @@ int i915_gem_object_unbind(struct drm_i915_gem_object *obj,
 		i915_vm_close(vm);
 		spin_lock(&obj->vma.lock);
 	}
-	list_splice(&still_in_list, &obj->vma.list);
+	list_splice_init(&still_in_list, &obj->vma.list);
 	spin_unlock(&obj->vma.lock);
 
 	if (ret == -EAGAIN && flags & I915_GEM_OBJECT_UNBIND_ACTIVE) {