update Sigmoid.bsv so it compiles again
update Sigmoid.bsv so it compiles again

Change-Id: I602305ddbbae12301fffd10f566797dae24aa39e

hanw/connectal,8l/connectal,chenm001/connectal,cambridgehackers/connectal,csail-csg/connectal,8l/connectal,8l/connectal,hanw/connectal,chenm001/connectal,cambridgehackers/connectal,hanw/connectal,chenm001/connectal,8l/connectal,cambridgehackers/connectal,chenm001/connectal,csail-csg/connectal,8l/connectal,hanw/connectal,chenm001/connectal,csail-csg/connectal,cambridgehackers/connectal,hanw/connectal,csail-csg/connectal,cambridgehackers/connectal,csail-csg/connectal