virtio: console: Register with sysfs and create a 'name' attribute for ports

The host can set a name for ports so that they're easily discoverable
instead of going by the /dev/vportNpn naming. This attribute will be
placed in /sys/class/virtio-ports/vportNpn/name. udev scripts can then
create symlinks to the port using the name.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/include/linux/virtio_console.h b/include/linux/virtio_console.h
index bd0e2a5..1ebf007 100644
--- a/include/linux/virtio_console.h
+++ b/include/linux/virtio_console.h
@@ -40,6 +40,7 @@
 #define VIRTIO_CONSOLE_CONSOLE_PORT	1
 #define VIRTIO_CONSOLE_RESIZE		2
 #define VIRTIO_CONSOLE_PORT_OPEN	3
+#define VIRTIO_CONSOLE_PORT_NAME	4
 
 #ifdef __KERNEL__
 int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int));