Stripping GTPU in eNB's M1-U.

srsenb/src/upper/gtpu.cc

@@ -428,6 +428,9 @@ void gtpu::mch_thread::run_thread()
 
     pdu->N_bytes = (uint32_t) n;
     
+    gtpu_header_t header;
+    gtpu_read_header(pdu, &header);
+
     pdcp->write_sdu(SRSLTE_MRNTI, lcid, pdu);
     do {
       pdu = pool_allocate;