drm/i915: initialize dpio_lock spin lock

This thing is killing lockdep.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
[Jani: move the init next to the other spin lock inits]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_dma.c

@@ -1587,6 +1587,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	spin_lock_init(&dev_priv->irq_lock);
 	spin_lock_init(&dev_priv->error_lock);
 	spin_lock_init(&dev_priv->rps_lock);
+	spin_lock_init(&dev_priv->dpio_lock);
 
 	if (IS_IVYBRIDGE(dev) || IS_HASWELL(dev))
 		dev_priv->num_pipe = 3;