doc: announce FIB configuration structure change

Announce addition of the flags field into rte_fib_conf structure.

Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>
Acked-by: Robin Jarry <rjarry@redhat.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>

doc/guides/rel_notes/deprecation.rst

@@ -166,6 +166,9 @@ Deprecation Notices
   The legacy actions should be removed
   once ``MODIFY_FIELD`` alternative is implemented in drivers.
 
+* fib: A new flag field will be introduced in ``rte_fib_conf`` structure
+  in DPDK 24.11. This field will be used to pass extra configuration settings.
+
 * cryptodev: The function ``rte_cryptodev_cb_fn`` will be updated
   to have another parameter ``qp_id`` to return the queue pair ID
   which got error interrupt to the application,