gprs_ns2: Introduce gprs_ns2_create_nse2() for SGSN side SNS

gprs_ns2_create_nse() doesn't allow the caller to specify if the
BSS or the SGSN role of IP-SNS shall be implemented.  Add
gprs_ns2_create_nse2() to fix that.

Change-Id: I6db8c36f7c69b592d7d0fbcf323804f7e9912be2
Related: OS#3373
diff --git a/include/osmocom/gprs/gprs_ns2.h b/include/osmocom/gprs/gprs_ns2.h
index 56a9b4f..be59a67 100644
--- a/include/osmocom/gprs/gprs_ns2.h
+++ b/include/osmocom/gprs/gprs_ns2.h
@@ -158,6 +158,9 @@
 struct gprs_ns2_nse *gprs_ns2_create_nse(struct gprs_ns2_inst *nsi, uint16_t nsei,
 					 enum gprs_ns2_ll linklayer,
 					 enum gprs_ns2_dialect dialect);
+struct gprs_ns2_nse *gprs_ns2_create_nse2(struct gprs_ns2_inst *nsi, uint16_t nsei,
+					 enum gprs_ns2_ll linklayer,
+					 enum gprs_ns2_dialect dialect, bool local_sgsn_role);
 uint16_t gprs_ns2_nse_nsei(struct gprs_ns2_nse *nse);
 void gprs_ns2_free_nse(struct gprs_ns2_nse *nse);
 void gprs_ns2_free_nses(struct gprs_ns2_inst *nsi);