gprs_bssgp: Add bssgp_tx_bvc_reset2()

If a BVC-RESET is sent from SGSN, there must not be a cell ID IE
included.  See "Note 1" of TS 48.018 Section 10.4.12.

Change-Id: I11d4e70d510265b9c09dffccdab10b3f0816715a
diff --git a/src/gb/gprs_bssgp_bss.c b/src/gb/gprs_bssgp_bss.c
index 5c9d11c..5a1ffb9 100644
--- a/src/gb/gprs_bssgp_bss.c
+++ b/src/gb/gprs_bssgp_bss.c
@@ -290,7 +290,7 @@
 }
 
 /*! Transmit a BVC-RESET message (Chapter 10.4.12) */
-int bssgp_tx_bvc_reset(struct bssgp_bvc_ctx *bctx, uint16_t bvci, uint8_t cause)
+int bssgp_tx_bvc_reset2(struct bssgp_bvc_ctx *bctx, uint16_t bvci, uint8_t cause, bool add_cell_id)
 {
 	struct msgb *msg = bssgp_msgb_alloc();
 	struct bssgp_normal_hdr *bgph =
@@ -306,7 +306,7 @@
 
 	msgb_tvlv_put(msg, BSSGP_IE_BVCI, 2, (uint8_t *) &_bvci);
 	msgb_tvlv_put(msg, BSSGP_IE_CAUSE, 1, &cause);
-	if (bvci != BVCI_PTM) {
+	if (add_cell_id) {
 		uint8_t bssgp_cid[8];
 		bssgp_create_cell_id(bssgp_cid, &bctx->ra_id, bctx->cell_id);
 		msgb_tvlv_put(msg, BSSGP_IE_CELL_ID, sizeof(bssgp_cid), bssgp_cid);
@@ -315,6 +315,10 @@
 
 	return gprs_ns_sendmsg(bssgp_nsi, msg);
 }
+int bssgp_tx_bvc_reset(struct bssgp_bvc_ctx *bctx, uint16_t bvci, uint8_t cause)
+{
+	return bssgp_tx_bvc_reset2(bctx, bvci, cause, bvci != BVCI_PTM);
+}
 
 /*! Transmit a FLOW_CONTROL-BVC (Chapter 10.4.4)
  *  \param[in] bctx BVC Context