gprs_bssgp: add handling for BSSGP RIM primitives

Receive and forward RIM messages to bssgp_prim_cb()

Change-Id: Idfd0a65872a2cc6089885afd8d31b0b029d85d47
Related: SYS#5103
diff --git a/include/osmocom/gsm/prim.h b/include/osmocom/gsm/prim.h
index e7a60e3..045e353 100644
--- a/include/osmocom/gsm/prim.h
+++ b/include/osmocom/gsm/prim.h
@@ -16,4 +16,6 @@
 	SAP_BSSGP_PFM,
 
 	SAP_NS,
+
+	SAP_BSSGP_RIM,
 };