drm/i915: Capture interesting display registers on error

When trying to diagnose mysterious errors on resume, capture the
display register contents as well.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -729,6 +729,9 @@ static int i915_error_state(struct seq_file *m, void *unused)
 	if (error->overlay)
 		intel_overlay_print_error_state(m, error->overlay);
 
+	if (error->display)
+		intel_display_print_error_state(m, dev, error->display);
+
 out:
 	spin_unlock_irqrestore(&dev_priv->error_lock, flags);