Fix Coverity Scan CID 339964 (Passing &rrc_eNB_mui to function...

Fix Coverity Scan CID 339964 (Passing &rrc_eNB_mui to function rrc_eNB_process_S1AP_DOWNLINK_NAS which uses it as an array. This might corrupt or misinterpret adjacent memory locations.)

openair2/RRC/LTE/rrc_eNB_S1AP.c

@@ -918,7 +918,7 @@ rrc_eNB_process_S1AP_DOWNLINK_NAS(
     rrc_data_req (
       &ctxt,
       srb_id,
-      *rrc_eNB_mui++,
+      (*rrc_eNB_mui)++,
       SDU_CONFIRM_NO,
       length,
       buffer,