qmp: Add QMP query-named-block-nodes to list the named BlockDriverState nodes.

Signed-off-by: Benoit Canet <benoit@irqsave.net>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/blockdev.c b/blockdev.c
index 386109a..0bfe380 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1952,6 +1952,11 @@
     }
 }
 
+BlockDeviceInfoList *qmp_query_named_block_nodes(Error **errp)
+{
+    return bdrv_named_nodes_list();
+}
+
 #define DEFAULT_MIRROR_BUF_SIZE   (10 << 20)
 
 void qmp_drive_mirror(const char *device, const char *target,