hvc_console: Add a hangup notifier for backends

I have added a hangup notifier that can be used by hvc console
backends to handle a tty hangup. The default irq hangup notifier
calls the notifier_del_irq() for compatibility.

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/drivers/char/hvc_iseries.c b/drivers/char/hvc_iseries.c
index b71c610..b74a2f8 100644
--- a/drivers/char/hvc_iseries.c
+++ b/drivers/char/hvc_iseries.c
@@ -202,6 +202,7 @@
 	.put_chars = put_chars,
 	.notifier_add = notifier_add_irq,
 	.notifier_del = notifier_del_irq,
+	.notifier_hangup = notifier_hangup_irq,
 };
 
 static int __devinit hvc_vio_probe(struct vio_dev *vdev,