gb: Fix missing exporting symbol bssgp_encode_rim_pdu

The symbol was not in the list of exported symbols.

Change-Id: I4c3792c3b22989571548e40aa4fbf26912e699df
diff --git a/src/gb/libosmogb.map b/src/gb/libosmogb.map
index db638f9..ff5b34a 100644
--- a/src/gb/libosmogb.map
+++ b/src/gb/libosmogb.map
@@ -20,6 +20,7 @@
 bssgp_enc_ran_inf_app_cont_nacc;
 bssgp_enc_ran_inf_app_err_rim_cont;
 bssgp_enc_ran_inf_rim_cont;
+bssgp_encode_rim_pdu;
 bssgp_fc_in;
 bssgp_fc_init;
 bssgp_fc_ms_init;