drm/i915: correct lock type in destroy

This is only relevant when using module unloading, and really only helps
get rid of a probably benign warning.

I can't remember if I sent this out already, but it's not turning up in
any of my searches.
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -1017,11 +1017,12 @@ void i915_destroy_error_state(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct drm_i915_error_state *error;
+	unsigned long flags;
 
-	spin_lock(&dev_priv->error_lock);
+	spin_lock_irqsave(&dev_priv->error_lock, flags);
 	error = dev_priv->first_error;
 	dev_priv->first_error = NULL;
-	spin_unlock(&dev_priv->error_lock);
+	spin_unlock_irqrestore(&dev_priv->error_lock, flags);
 
 	if (error)
 		i915_error_state_free(dev, error);