osmo_io: Add function to change the maximum length of the tx_queue

Change-Id: If3d1de8bffe1123002515878655ea9e02b482888
diff --git a/src/core/libosmocore.map b/src/core/libosmocore.map
index 50be67c..99be86c 100644
--- a/src/core/libosmocore.map
+++ b/src/core/libosmocore.map
@@ -268,6 +268,7 @@
 osmo_iofd_set_data;
 osmo_iofd_set_ioops;
 osmo_iofd_set_priv_nr;
+osmo_iofd_set_txqueue_max_length;
 osmo_iofd_setup;
 osmo_iofd_txqueue_clear;
 osmo_iofd_txqueue_len;