gprs_bssgp_rim: allow sending of encoded RIM messages

The API function bssgp_tx_rim() accepts decoded RIM PDU structs, encodes
them and eventually sends them. However, there may be cases where the
RIM PCU already exists in its encoded form. (This is in particular the
case when the RIM PDU is forwarded from GTP to BSSGP)

Lets add an API function bssgp_tx_rim_encoded to allow sending of
already encoded RIM PDUs

Related: OS#6095
Change-Id: Id4a793bbaf32d7b9d894dcc5be3faaf2f2d91d82
diff --git a/src/gb/libosmogb.map b/src/gb/libosmogb.map
index e02273d..7dc427b 100644
--- a/src/gb/libosmogb.map
+++ b/src/gb/libosmogb.map
@@ -56,6 +56,7 @@
 bssgp_tx_resume_ack;
 bssgp_tx_resume_nack;
 bssgp_tx_rim;
+bssgp_tx_rim_encoded;
 bssgp_tx_simple_bvci;
 bssgp_tx_status;
 bssgp_tx_suspend;