Stripping GTPU in eNB's M1-U.

srsenb/src/upper/gtpu.cc

@@ -427,6 +427,9 @@ void gtpu::mch_thread::run_thread()
     } while (n == -1 && errno == EAGAIN);
 
     pdu->N_bytes = (uint32_t) n;
+    
+    gtpu_header_t header;
+    gtpu_read_header(pdu, &header);
 
     pdcp->write_sdu(SRSLTE_MRNTI, lcid, pdu);
     do {