vt: invoke notifier on screen size change

User space using poll() on /dev/vcs devices are not awaken when a
screen size change occurs. Let's fix that.
Signed-off-by: NNicolas Pitre <nico@linaro.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/vt/vt.c

@@ -1272,6 +1272,7 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc,
 	if (con_is_visible(vc))
 		update_screen(vc);
 	vt_event_post(VT_EVENT_RESIZE, vc->vc_num, vc->vc_num);
+	notify_update(vc);
 	return err;
 }