sgsn: Only look at TLLIs in sgsn_mm_ctx_by_tlli

Currently the code also matches the TLLI against LOCAL and FOREIGN
mappings of the P-TMSI, thus eventually finding MM contexts not
consistent with the TLLI (both tlli and tlli_new differ). On
the other hand, tlli_new is not checked at all.

This commit changes the function to only look at mmctx->tlli,
mmctx->tlli_new, and the routing area.

Sponsored-by: On-Waves ehf
diff --git a/openbsc/tests/sgsn/sgsn_test.c b/openbsc/tests/sgsn/sgsn_test.c
index 6d7ba38..2098972 100644
--- a/openbsc/tests/sgsn/sgsn_test.c
+++ b/openbsc/tests/sgsn/sgsn_test.c
@@ -1607,7 +1607,7 @@
  */
 static void test_gmm_ptmsi_allocation(void)
 {
-	struct gprs_ra_id raid = { 0, };
+	struct gprs_ra_id raid = {332, 112, 16464, 96};
 	struct sgsn_mm_ctx *ctx = NULL;
 	struct sgsn_mm_ctx *ictx;
 	uint32_t foreign_tlli;