vty: Forward delcare the logging command.
diff --git a/include/osmocom/vty/logging.h b/include/osmocom/vty/logging.h
index f8ffbc3..45d74fd 100644
--- a/include/osmocom/vty/logging.h
+++ b/include/osmocom/vty/logging.h
@@ -4,4 +4,6 @@
 #define LOGGING_STR	"Configure log message to this terminal\n"
 #define FILTER_STR	"Filter log messages\n"
 
+void logging_vty_add_cmds(void);
+
 #endif /* _VTY_LOGGING_H */