gprs_ns2: always pass a tp to gprs_ns2_vc_rx

In preparation of checking the NSEI/NSVCI in ns2_vc_rx. It
makes the function less error prone as the *tp is always defined.

Change-Id: I3cd6ed20cdc1390075669e1d0101154c51f3997f
diff --git a/src/gb/gprs_ns2.c b/src/gb/gprs_ns2.c
index ec60dbd..451290b 100644
--- a/src/gb/gprs_ns2.c
+++ b/src/gb/gprs_ns2.c
@@ -1047,7 +1047,7 @@
 		struct msgb *msg)
 {
 	struct gprs_ns_hdr *nsh = (struct gprs_ns_hdr *) msg->l2h;
-	struct tlv_parsed tp;
+	struct tlv_parsed tp = { };
 	int rc = 0;
 
 	log_set_context(LOG_CTX_GB_NSE, nsvc->nse);
@@ -1099,7 +1099,7 @@
 		break;
 
 	case NS_PDUT_UNITDATA:
-		rc = gprs_ns2_vc_rx(nsvc, msg, NULL);
+		rc = gprs_ns2_vc_rx(nsvc, msg, &tp);
 		break;
 	default:
 		rc = ns2_tlv_parse(&tp, nsh->data,