drm/nv50: punt hotplug irq handling out to workqueue

On DP outputs we'll likely end up running vbios init tables here, which
may sleep.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/nv50_display.h b/drivers/gpu/drm/nouveau/nv50_display.h
index 3ae8d07..581d405 100644
--- a/drivers/gpu/drm/nouveau/nv50_display.h
+++ b/drivers/gpu/drm/nouveau/nv50_display.h
@@ -37,6 +37,7 @@
 
 void nv50_display_irq_handler(struct drm_device *dev);
 void nv50_display_irq_handler_bh(struct work_struct *work);
+void nv50_display_irq_hotplug_bh(struct work_struct *work);
 int nv50_display_init(struct drm_device *dev);
 int nv50_display_create(struct drm_device *dev);
 int nv50_display_destroy(struct drm_device *dev);