vty_app_info.is_config_node: add OSMO_DEPRECATED

Although this OSMO_DEPRECATED doesn't seem to generate a warning when compiling
code that sets .is_config_node = foo, it seems a good idea to add the
deprecation tag.

It is deprecated since commit "vty: track parent nodes also for telnet sessions"
I2b32b4fe20732728db6e9cdac7e484d96ab86dc5

Change-Id: I800507b27cb0d536c1a4c203d7f7b90eec05a69c
diff --git a/include/osmocom/vty/vty.h b/include/osmocom/vty/vty.h
index 9acaa7d..b63dc3b 100644
--- a/include/osmocom/vty/vty.h
+++ b/include/osmocom/vty/vty.h
@@ -5,6 +5,7 @@
 #include <stdbool.h>
 
 #include <osmocom/core/linuxlist.h>
+#include <osmocom/core/defs.h>
 
 /*! \defgroup vty VTY (Virtual TTY) interface
  *  @{
@@ -186,7 +187,9 @@
 	int (*go_parent_cb)(struct vty *vty);
 	/*! OBSOLETED: Implicit parent node tracking has replaced the use of this callback. This callback is no longer
 	 * called, ever, and can be left NULL. */
-	int (*is_config_node)(struct vty *vty, int node);
+	int (*is_config_node)(struct vty *vty, int node)
+		OSMO_DEPRECATED("Implicit parent node tracking has replaced the use of this callback. This callback is"
+				" no longer called, ever, and can be left NULL.");
 	/*! Check if the config is consistent before write */
 	int (*config_is_consistent)(struct vty *vty);
 };