fixed compiler warning when timesynch is disabled
fixed compiler warning when timesynch is disabled

arurke/contiki,MohamedSeliem/contiki,bluerover/6lbr,arurke/contiki,arurke/contiki,arurke/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,bluerover/6lbr,arurke/contiki,bluerover/6lbr,bluerover/6lbr,MohamedSeliem/contiki,bluerover/6lbr,arurke/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,bluerover/6lbr,MohamedSeliem/contiki,bluerover/6lbr,arurke/contiki