[nat] Ignore paging that is to page by BSS...

We do not want to handle this identity. If we can not page by
lac there is no need to page anything else.
diff --git a/openbsc/src/nat/bsc_nat_utils.c b/openbsc/src/nat/bsc_nat_utils.c
index 0815a4a..28b1bc7 100644
--- a/openbsc/src/nat/bsc_nat_utils.c
+++ b/openbsc/src/nat/bsc_nat_utils.c
@@ -127,7 +127,11 @@
 
 	data_length = TLVP_LEN(&tp, GSM0808_IE_CELL_IDENTIFIER_LIST);
 	data = TLVP_VAL(&tp, GSM0808_IE_CELL_IDENTIFIER_LIST);
-	if (data[0] !=  CELL_IDENT_LAC) {
+
+	/* No need to try a different BSS */
+	if (data[0] == CELL_IDENT_BSS) {
+		return NULL;
+	} else if (data[0] != CELL_IDENT_LAC) {
 		LOGP(DNAT, LOGL_ERROR, "Unhandled cell ident discrminator: %d\n", data[0]);
 		return NULL;
 	}